Mindreading will not significantly impair your ability to level. I've mindread pretty much everyone in DKS, and will still be level 37 before heading to the Hall of Echoes.
The experience cost for a mindread that gives a skill or stat point is a fairly small fraction of the experience needed to reach a new level, so is always worth it, IMO. In D2:ED I reloaded so I didn't waste experience on useless mindreads, but since useless mindreads are generally cheap and those that just give loot are not too expensive, it really doesn't matter much in the end. In D2:ED I went to the Hall of Echoes at level 36.5 without doing too much to try to get to a high level. In DKS I did everything I could to maximize experience (without learning Wisdom or avoiding mindreading) and still am not going to get much past level 37. Even then, part of the difference is due to balancing changes made in DKS, rather than what I did.
You get more experience from opponents at a lower level, so part of the mindread experience debt is compensated for by getting a little extra experience from opponents, compared to what you would have if you leveled sooner.
In the FoV section of the game mindreading is required for a lot more quests, and gives lots of skill points in return, so you should fairly easily be able to max the Mindread skill. Also, there are caves with respawning opponents, so there is a steady (if potentially boring) supply of experience.
