Although it may be possible to turn a profit with crafted items in Ch 3, I've never noticed that it could be done. The example MrZork furnished may be the rare exception but never tried it by maxing Appraise which may make a difference. But just for standard Appraise levels (zero plus INT modifier), the crafting process is not equitable in Ch 3 unless you plan to use the item. However, in Ch 1, craft as many of the items as you can and pay attention to the relative values because it may be better to craft items with higher intrinsic resultant value with those extremely rare components (like adamantine). If in doubt which might be the better profit, save before crafting each, note the final value and reload using a different item if it is not all that impressive, saving the rare component for a better choice. (BTW, Durga has some of the highest "buy" rates around so is handy to use for crafting comparison.)
The only other restrictive quest that comes to mind is the Tamora quest for some minor XP, but that one is gender-specific rarther than class-specific. Also, to get all the druid circle combat opportunities you will need at least druid 7. (XP/loot can be mined in those battles by dropping the intermediary rewards temporarily.)
Allocation to certain rogue skills (sry, cannot recall which ones are checked atm
'> ) are needed to gain access to Blackmarket/covert item vendors beginning in Ch 2 (IIRC). The one run by Torgo in Ch 1 Moonstone Mask is usable by all skill sets.
The magic lab in Ch 2 can be used by any class that has allocated to UMD with the proviso that they procure the necessary components, wands, rods, scrolls or other items to cast spells on the container. There are never any XP rewards for the lab creation activities, however.
There are no class-specific activities other than for arcanist classes and druids, though clerics can perform a few peripheral class-specific actions in a few places that also provide no XP, just minor advantages.