I think I've found another problem with LotRO for Mac.
The FPS limiter in Troubleshooting section does not seem to work (at least not for me). My Macbook Air (mid-2012) seems to be able to handle mideium settings just fine, however, without being able to limit my FPS I am getting unacceptably high temperatures (had the same issue with WoW for Mac, was completely solved with limiting my foreground FPS to 30 and background FPS to 0).
Even if I limit FPS to 15 in LotRO, it seems to have no effect, the framerate reamains the same.
Probably, there is a way to address the issue.