If I try and install more than one skill-adding mod, the skills from one of them just show up twice. One of them winds up being dominant for some reason, and so even if I don't load it using the mod loader in the launcher, the dominant one ends up replacing it, as long as it's so much as in the mod folder.
I am also reasonably sure I did indeed install the mods correctly, as I can use a single one just fine.
I am also having a similar issue, with the "dominant" mod being the final one on the list. This seems to be on all Mac platforms, as I'm on Lion with a similar issue. This I doubt is human error.
This is an example of the bug. I tried to use essential skills I, clockwork knight and my swiftstriker skill trees, but what I got was three swiftstrikers with the graphics of the clockwork knight.