I've recently been experimenting with PLO GTO trainer. In many situations, there is a tiny difference in EV between call and raise. However, call might be used 95% of the time vs 5% for raise.

My question is: if a player consistently over-raises in this situation (frequencies are imbalanced), is that a major problem that can be exploited? Or, is it just a "small problem" because the EV loss is so small compared to bigger blunders?

The corollary would be: What if my frequencies are correct, but I use the wrong hands. What's the bigger blunder: Wrong frequencies or wrong hands?

Wrong hands would be a bigger mistake than wrong frequencies.

Some things to keep in mind:

If two or more actions are mixed, then they equal EV (or the sim is not converged).

If you are doing an action that is mixed, but at the wrong frequency, then the only way for you to lose EV is for your opponent to adjust his strategy in future hands to exploit that frequency difference. For example, if you *always* called all your 0EV bluff catchers then your opponent could simply stop bluffing or value bet thinner potentially. You should also realize your opponents are not playing like a solver. Doing stuff with the wrong hands is usually just going to be an EV loss as other actions have higher EV.

Gotcha, thanks! So, if Villain is playing GTO, then I won't lose EV if I use the wrong frequencies on mixed action hands. But I would become more exploitable.

This is a correct statement, yes.

Against a GTO bot your frequencies don't matter, assuming both actions have equivalent EV, but against a human whose frequencies are typically imbalanced one way or another your frequencies do matter.

If they bluff too much and you fold too much you will get crushed. If they don't bluff enough and you call too much you will get crushed.

That's the whole idea of being balanced. Whether they always have it or never have it they won't gain an edge on you if you call at the optimal frequency.