I got that issue that a rotated text looks washed when you use the package:
\usepackage[T1]{fontenc}
Sadly I can't reject the fontenc-package because it has a lot of dependencies to the rest of the project. Is there any workaround to handle this problem?
without package:
with package:
Example:
\documentclass[a4paper,10pt]{article}
%FONTS
\usepackage[T1]{fontenc}
%TIKZ LIBRARYS
\usepackage{tikz}
\usetikzlibrary{positioning,shapes,shadows,arrows,backgrounds}
\tikzstyle{arrow}=[->, >=open triangle 60, thick, color=black]
\begin{document}
\begin{tikzpicture}
\draw[arrow, rounded corners] (0,0) -- node[sloped, anchor=center, above] {I have a} node[sloped, anchor=center, below] {washed style :(} (-4,-4);
\end{tikzpicture}
\end{document}


