I guess I'll start this off by saying in advance that I like this game. I'm just going to type whatever issues come to mind that I have found over the course of my gameplay.
Enemies take way too long to kill. I've been playing on the master hero difficulty and it's just either finding a position that I can sit in and continuously attack to kill the enemy over a boringly long period of time, or dodge while killing them over a boringly long period of time. This was beginning to not be such a problem when I started using creeping death and miasma whip more often in combination with my usual energy orb and ball lightning combo. I could dump my mana out into quick, piercing damage with creeping death and then follow up with the usual combo. Miasma whip+energy orb was great for killing utahraptors or other electric resistant dudes. And I'm pretty unkillable due to the shield spells being..really way too good. When the overload and conserving mind enchants were nerfed the time for me to actually kill enemies like doubled at least. This hasn't made combat any harder, just take way longer. Things with bucketloads of health are even worse, but even enemies with low HP feel like they take too long to kill. The problem isn't that these enchants are horrible now or anything, they were really way too good before. It's just the underlying problem of enemies taking way too long to kill. Oh and MULTIPLYING enemy health by player count is pretty absurd, just gonna throw that in there. That only really works with the assumption that everyone is always going to be focusing fire on the target... And that's still pretty ridiculous when it's going to take as long as it does now for EVERYONE to kill one dude. I think it is ok if having friends come with you is an advantage somewhat, rather than just scaling completely evenly.
Knockback is pretty useless outside of meteor missions because like half or more of all enemies are immune. Some flying melee enemies can be knocked back, which is good, but that's pretty much the only other use. I like to knock espers/amoebae into a corner so I can wail on them til they die and not have to re-adjust my aim throughout the long process, but that's not really that amazing of a tactic. When it comes down to it, most of the melee enemies are the ones you'd WANT to knock back. But all the ground ones and some flying ones are just immune entirely... If these enemies corner me I just tank a hit with a shield to get into a position where I can resume dodging, so it's not like knockback immunity is unbeatable (unless they're just huge, like sea worms, and you're indoors so they take up the whole passage). But overall it feels knockback is really not as useful as it should be. I know it's hard to balance since a lot of enemies become ridiculously tame if you can just hold M1 and they can never reach you, but still I thought I should mention that.
Actually nothing else major is coming to mind right now besides those things. I'm sure there's more but I just can't remember right now. For now I will leave this topic here and see what everyone thinks.