It's been removed.

I've seen that one, wasn't interested since it changed all of the skills trees instead of just focusing on the common skill tree

Might've broken with the update or maybe it never did anything lol either way there's a better mod than this one now, by Melody.

The Thick Skinned ability doesn't seem to actually do anything. The defense of both my heroes and units both stay the same when putting points into it, it might have to do with my hero being a governor and I'm also using ELCP

Not a bad idea.

That approach does make sense.
It might be a better idea for Siege Mentality(and maybe Defender) to reduce their lvls, but increase the effect.
You get more for a single point, but cannot put a 2nd point into it. This makes sense, as EL favors stacking the same effect over and over, which can lead to OP shit. This makes the point stronger and removes something largely unused(the 2nd point) to insulate vs the problem that can come from stacking stats.

It's a big increase, but the top players were all saying they're worthless before, and they liked my changes so idk. I'd rather make something that has a noticeable impact so I can gather feedback.

Hmm, true, considering ELCP, it would make sense to buff Siege Mentality a tad more.

With Indiana Bones or No Idle Hands, I am merely worried that either could lead to some unhealthy strategies(No Idle Hands especially). I am probably overreacting there, cause the powerlevel of their effects is difficult to judge.

Bear in mind they're available to everyone.

Fortification and retaliation have been buffed substantially in ELCP. Retaliation was just buffed in the latest beta. Defenders have a big advantage with ELCP fortification rules.

I buffed defender and siege mentality both, but made them more situational.

Maybe, but the top players approved.

Sure, use whatever you want.

Small, but good changes. Definitely makes the tree a little more interesting. A few things:
Indiana Bones buff is quite substantial and maybe not the right call. Strong early ruins are very good at giving you a headstart.
Idle Hands does not need a buff... Especially due to the Drakken strategy(Fast Leaner+No Idle hands is rather powerful). It could give +1 extra xp per lvl to the hero, that might be fine.
I like your Siege Mentality and Defender changes. However, +15% initiative is really strong. I'd rather just buff the +atk to 20% per lvl.

Lastly, I'll probably use your defender/Siege mentality changes in a skill-tree mod I am currently working on, if that is fine for you.