The problem with making classes that are different combinations of stats is...

All the main attributes are basically the exact same thing with different names: they all increase potency of attacks. Vitality and Piety are the only exceptions to this. Adding in new classes with different combinations of stats wouldn't really provide variety in terms of design and only serve to increase loot bloat on bosses. Think about it - how is Strength functionally different from Dexterity? Or Intelligence? They're not. They're useful for X, Y, and Z classes to increase damage and useless to everyone else.

In order to get variety in classes via stats, you need to base it off stats that all classes can use that actually do different things, which either means making Crit, Skill/Spellspeed, and the others more relevant, or revamping the main attributes entirely. To see an example, we can look at WildStar's stats. Assault Power and Support Power are the "raw throughput" stats - either increasing damage for assault abilities or increasing damage/healing for support abilities. The other stats - Multihit, Crit, Crit Severity, Vigor, Intensity, etc - are pretty much all useful to all classes in varying combinations and priorities.

I'm probably getting way off-topic, but the mention of new classes and different combos of main attributes just stirred a thought. xD