1 - Buff WT3 bonus, simple as that… If people feel that leveling from 50 to 66 or 70 is too slow buff the WT3 bonus (guess doesn’t make sense to have a 100% bonus XP and struggle and then hit a threshold where you gain 200% bonus, so simply buff WT3 to 150 or even 175%)
2 - Add assymetry to what’s good vs what, not always a “more dps solves the problem” in terms of targetted impact… Add 2 types of armor (much like elite and non-elite, add 2 types of armor on mobs like in SC - light and heavy armor)… This would solve a lot of problems with “game too easy” or “game too grindy”, you’re good vs what you spec and struggle vs what you’re not speccing into
For example Incinerate should feel really good vs Spirits but struggle vs Bears, Fireball should have the opposite effect (somewhat), same with other skills, can really find a way how things are “intuitive” of what works vs what and what doesnt… Pulverize should be good against Bears, Wolves, and basically things that are “solid” overall, Shred should feel better against flies, spirits, casters more…
Spend a month or two and analyze each skill to how can the skill contribute to a greater specialization (or vice versa, which mob could “tank” or “evade” or “absorb” a certain skill), for example Knights could “tank” flurry but feel the pain from Twisting Blades and perhaps the player couldn’t even realize there were flies around when casting a flurry and a bunch of flies or bats happened to be at the wrong time in a wrong spot 
Spend that time of introducing some asymmetry, on the long run would bring much worth, even more so than adding new content overall… Have us have that feel of cat & mouse game between killing light/unarmored/mobile things fast or simply “sniping down” a big dude but struggle vs the other
Just by adding that kind of “wrench” of partionalizing targetted impact of damage and impact of certain things itemization can be affected in a much interesting way also