See, if the following solution is close to ones you looking for:

To your MWE I add showframe (for see page layout, in real use it should be omitted), options font=small and justification=RaggedRight to package caption (with this the height of images is slightly reduced) and usetwo image environment for hack to obtain desired form of page. Package lipsum is for dummy text.
\documentclass[letterpaper,twocolumn]{article}
\usepackage{mathptmx} % Times Roman for text *and* math
\usepackage{times}
\usepackage{helvet}
\usepackage{courier}
\usepackage{graphicx}
\usepackage[font=small,justification=RaggedRight]{caption}% <-- added options
\frenchspacing
\setlength{\pdfpagewidth}{8.5in}
\setlength{\pdfpageheight}{11in}
\usepackage{ragged2e}% <-- new
\usepackage{lipsum}% <-- in real use should be omitted
\usepackage{showframe}% <-- in real use should be omitted
\begin{document}
\lipsum[1-3]
\begin{figure*}[t!]
\begin{minipage}[b]{.22\linewidth}
\includegraphics[width=\columnwidth]{example-image}
\caption{Day1: 02-Nov-2014: Adverse Event Count = 106 (time duration 08:50) Max Excursion= 3.96° DF}\label{label-a}
\end{minipage}
\hfill
\begin{minipage}[b]{.22\linewidth}
\includegraphics[width=\columnwidth]{example-image}
\caption{Day14: 15-Nov-2014: Adverse Event Count = 107 (time duration 08:55) Max Excursion= 1.95° F
}\label{label-b}
\end{minipage}
\hfill
\begin{minipage}[b]{.22\linewidth}
\includegraphics[width=\columnwidth]{example-image}
\caption{Day15: 16-Nov-2014: Adverse Event Count = 103 (time duration 08:35) Max Excursion= 3.96° F
}\label{label-a}
\end{minipage}
\hfill
\begin{minipage}[b]{.22\linewidth}
\includegraphics[width=\columnwidth]{example-image}
\caption{Day16: 17-Nov-2014: Adverse Event Count = 7 (time duration 00:35) Max Excursion= 0.94° F
}\label{label-b}
\end{minipage}
\begin{minipage}[b]{.22\linewidth}
\includegraphics[width=\columnwidth]{example-image}
\caption{Day19: 20-Nov-2014: Adverse Event Count = 8 (time duration 00:40) Max Excursion= 0.94° F
}\label{label-a}
\end{minipage}
\hfill
\begin{minipage}[b]{.22\linewidth}
\includegraphics[width=\columnwidth]{example-image}
\caption{Day22: 22-Nov-2014: Adverse Event Count = 75 (time duration 06:15) Max Excursion= 0.94° F
}\label{label-b}
\end{minipage}
\hfill
\begin{minipage}[b]{.22\linewidth}
\includegraphics[width=\columnwidth]{example-image}
\caption{Day23: 23-Nov-2014: Adverse Event Count = 114 (time duration 09:30) Max Excursion= 4.98° F
}\label{label-a}
\end{minipage}
\hfill
\begin{minipage}[b]{.22\linewidth}
\includegraphics[width=\columnwidth]{example-image}
\caption{Day24: 24-Nov-2014: Adverse Event Count = 8 (time duration 00:40) Max Excursion= 0.94° F
}\label{label-b}
\end{minipage}
\begin{minipage}[b]{.22\linewidth}
\includegraphics[width=\columnwidth]{example-image}
\caption{Day25: 25-Nov-2014: Adverse Event Count = 12 (time duration 01:00) Max Excursion= 1.04° F}\label{label-a}
\end{minipage}
\hfill
\begin{minipage}[b]{.22\linewidth}
\includegraphics[width=\columnwidth]{example-image}
\caption{Day26: 27-Nov-2014: Adverse Event Count = 8 (time duration 00:40) Max Excursion= 0.94° F}\label{label-b}
\end{minipage}
\hfill
\begin{minipage}[b]{.22\linewidth}
\includegraphics[width=\columnwidth]{example-image}
\caption{Day61: 01-Jan-2015: Adverse Event Count = 19 (time duration 01:35) Max Excursion= 0.57° F}\label{label-a}
\end{minipage}
\hfill
\begin{minipage}[b]{.22\linewidth}
\includegraphics[width=\columnwidth]{example-image}
\caption{Day73: 13-Jan-2015: Adverse Event Count = 23 (time duration 01:55) Max Excursion= 0.80° F
}\label{label-b}
\end{minipage}
\end{figure*}
\begin{figure}[h!]
\vskip1ex
\captionof*{figure}{Figure 9-20: Adverse Area Plots (Quantity Below 68.1 Degrees F) for all days containing adverse events. As per ACCEPT Adverse Event Paradigm, these events are only in testing/validation data-sets}
\vskip-5ex
\end{figure}
\lipsum[4-9]
\end{document}
As you can see, the MWE has two manual adjusting of vertical spaces in the second figure environment which serve only for common caption/comment for above figures.
Addendum: Above solution is based on assumption, that all figures should be tied to each other, i.e. without text between them and with common description in one column which follows immediately to them.
An easily looked over figures can be obtained with their organization into 4 x 3 matrix (as indicated in question} over two columns in environment figure* to which follow another one column figure with common explanation/caption. This is possible if the sum of the both figures height is smaller than permitted area for figures on one page. This was reason why in the caption is reduced size of fonts.
Another possibilities is organizing figures into two figure environments, where the second also contain common "caption" (see example below). This solution not guarantee that all images will appear in one page as this is case in above solution.
In second solution instead of minipages is used tabularx (evidently it can be used also in the first solution). First figure has option [t!] and the second [b!]. With this is achieved flow of figures.
\documentclass[letterpaper,twocolumn]{article}
\usepackage{mathptmx} % Times Roman for text *and* math
\usepackage{times,helvet,courier}
\usepackage{graphicx}
\usepackage[font=small,justification=RaggedRight]{caption}% <-- added options
\frenchspacing
\setlength{\pdfpagewidth}{8.5in}
\setlength{\pdfpageheight}{11in}
\usepackage{ragged2e}% <-- new
\usepackage{tabularx}% <-- new
\usepackage{lipsum}% <-- in real use should be omitted
\usepackage{showframe}% <-- in real use should be omitted
\begin{document}
\lipsum[1-3]
\begin{figure}[b!]
\begin{tabularx}{\columnwidth}{@{}*{2}{X}@{}}
\includegraphics[width=\linewidth]{example-image}
\caption{Day1: 02-Nov-2014: Adverse Event Count = 106 (time duration 08:50) Max Excursion= 3.96° DF}\label{label-a}
& \includegraphics[width=\linewidth]{example-image}
\caption{Day14: 15-Nov-2014: Adverse Event Count = 107 (time duration 08:55) Max Excursion= 1.95° F
}\label{label-b}
\\
\includegraphics[width=\linewidth]{example-image}
\caption{Day15: 16-Nov-2014: Adverse Event Count = 103 (time duration 08:35) Max Excursion= 3.96° F
}\label{label-b}
& \includegraphics[width=\linewidth]{example-image}
\caption{Day16: 17-Nov-2014: Adverse Event Count = 7 (time duration 00:35) Max Excursion= 0.94° F
}\label{label-c}
\\
\includegraphics[width=\linewidth]{example-image}
\caption{Day19: 20-Nov-2014: Adverse Event Count = 8 (time duration 00:40) Max Excursion= 0.94° F
}\label{label-a}
& \includegraphics[width=\linewidth]{example-image}
\caption{Day22: 22-Nov-2014: Adverse Event Count = 75 (time duration 06:15) Max Excursion= 0.94° F
}\label{label-d}
\end{tabularx}
\end{figure}
% second part
\begin{figure}[t!]
\begin{tabularx}{\columnwidth}{@{}*{2}{X}@{}}
\includegraphics[width=\linewidth]{example-image}
\caption{Day23: 23-Nov-2014: Adverse Event Count = 114 (time duration 09:30) Max Excursion= 4.98° F
}\label{label-e}
& \includegraphics[width=\linewidth]{example-image}
\caption{Day24: 24-Nov-2014: Adverse Event Count = 8 (time duration 00:40) Max Excursion= 0.94° F
}\label{label-f}
\\
\includegraphics[width=\linewidth]{example-image}
\caption{Day25: 25-Nov-2014: Adverse Event Count = 12 (time duration 01:00) Max Excursion= 1.04° F}\label{label-g}
& \includegraphics[width=\linewidth]{example-image}
\caption{Day26: 27-Nov-2014: Adverse Event Count = 8 (time duration 00:40) Max Excursion= 0.94° F}\label{label-h}
\\
\includegraphics[width=\linewidth]{example-image}
\caption{Day61: 01-Jan-2015: Adverse Event Count = 19 (time duration 01:35) Max Excursion= 0.57° F}\label{label-i}
& \includegraphics[width=\linewidth]{example-image}
\caption{Day73: 13-Jan-2015: Adverse Event Count = 23 (time duration 01:55) Max Excursion= 0.80° F
}\label{label-j}
\end{tabularx}\vskip-3ex
\captionof*{figure}{Figure 9-20: Adverse Area Plots (Quantity Below 68.1 Degrees F) for all days containing adverse events. As per ACCEPT Adverse Event Paradigm, these events are only in testing/validation data-sets}
\end{figure}
\lipsum[4-9]
\end{document}

Further improvement of figures look-out can be obtain with introduction of shortens for repeating text, for example AEC for Adverse Event Count, ME for Max Excursion, which meaning can be given in common "caption". Similarly can be replaced mount short names with number (for example 02-Nov-2011 --> 02-11-2014). With these the captions would become more compact and height of figures is reduced.
The code is self-explanatory. In the first solution only slightly differ from MWE in question, in the second solution main difference is in used tabularx, whic simplify code and make it more concise.
subcaptionorsubfigurepackages . – Fran Apr 26 '16 at 06:00