Thanks for bringing this to our attention and the solution. Building on KOMA will be discontinued in the future, but a solution for this case was found in the mrunix forum etc.:
Solved in English: http://latex.org/forum/viewtopic.php?f=48&t=29080&p=98202#p98201
Solved in German: http://mrunix.de/forums/showthread.php?77166-Schriftart-Inhaltsverzeichnis-vereinheitlichen&p=362451&viewfull=1#post362451
\documentclass[12pt,a4paper,index=totoc]{scrbook}
\usepackage[OT1]{eulervm}
\usepackage{classicthesis}
\usepackage{arsclassica}
%\usepackage{makeidx}
\begin{document}
\tableofcontents
\chapter{Capybara}
test\index{test} test \index{test2}
\begin{figure}
\caption{Test-Figure}
\end{figure}
\addchap{Wombat}
\addcontentsline{toc}{chapter}{\tocEntry{Tabellenverzeichnis}}
\listoffigures
\begin{theindex}
\end{theindex}
\end{document}
Now also in the wiki: https://bitbucket.org/amiede/classicthesis/wiki/browse/
Thanks for bringing this to our attention and the solution. Building on KOMA will be discontinued in the future, but a solution for this case was found in the mrunix forum etc.:
Solved in English: http://latex.org/forum/viewtopic.php?f=48&t=29080&p=98202#p98201
Solved in German: http://mrunix.de/forums/showthread.php?77166-Schriftart-Inhaltsverzeichnis-vereinheitlichen&p=362451&viewfull=1#post362451
Now also in the wiki: https://bitbucket.org/amiede/classicthesis/wiki/browse/