I adapted this answer to make a custom section I need. My intention is that it looks something like the second heading from this image:

So the numbering must be made using (\Alph) and it must be independent from the section/subsection. The counter should restart at each subsection.
Here's a MWE with my attempt to achieve the heading I need:
\documentclass{article}
\usepackage{titlesec}
%%% seccion para estatica comparativa
\titleclass{\scenario}{straight}[\subsection]
\newcounter{scenario}[subsection]
\titleformat{\scenario}
{\scshape}{}{0em}{(\thescenario)~}
\titlespacing*{\scenario}{0pt}{3.25ex plus 1ex minus .2ex}{1.5ex plus .2ex}
\renewcommand*{\thescenario}{\Alph{scenario}}
\newcommand{\scenarioautorefname}{scenario}
\begin{document}
\setcounter{tocdepth}{1}
\tableofcontents
\section{First section}
\subsection{First subsection}
\scenario{My first scenario}
\scenario{My second scenario}
\subsection{Second subsection}
\scenario{My third scenario}
Counter restarts.
\end{document}
I'm sure that I must be making some mistake, because even though it produces the desired result, now the TOC compiles incorrectly, showing the scenarios even though I defined TOC depth to 1.
What mistake am I making on the definition of the custom heading? I tried looking on this site or the titlesec documentation, but haven't been able to solve it.

titleseccould pinpoint the mistake just by looking at the definition of the custom heading, so that a MWE wouldn't be necessary. Sorry, I updated my question accordingly. – han-tyumi Aug 22 '14 at 21:52titlesecsince every time I try, I find it turns out to create more problems than it solves. However, I know it works well for others. – cfr Aug 22 '14 at 22:35\titleclasscommand doesn't appear to do what it says on the tin. According to the documentation, it should mean\scenariois level 2 and\subsectionis level 3. Yet that does not appear to be the case at all... – cfr Aug 22 '14 at 23:00