Parmandur
Book-Friend, he/him
What problems, specifically?
I'm particularly interested in any that aren't the results of general rules bloat, and aren't the result of problems with other systems or classes which just interact poorly with a class.
Personally in 3.XE I fully expected to see problems with the number of classes, especially post Tome of Nine Fighter Replacements or whatever it was called, but they never actually materialised. So I'm curious.
PRCs caused huge problems, but they aren't classes, and it was largely a double handful of specific, broken PRCs, mostly from early 3E days which were at the heart of every PRC issue. Bloat was only a problem with them in that 80% were simply bad choices.
Analysis paralysis, and neccesitating a serious deep dive into "builds" to make the desired character for most people. I'm lumping in PRC with Class's, since a Class is a Class. That 80% were worthless choices is something I agree with, and is the point.
In 5E, in contrast, there is basically no "wrong" choice, just choices that are more or less interesting to an individual. Having a small, curated number of base Classes with 12 (now 13) strict patterns for Subclass design helps channel design into useable choices.