In general I like the addition of this concentration feature. But it should be improved, eg. like "The Red Queen" above said and maybe some spells should replace concentration with a fixed "lasts x rounds" instead.
But I like it eg. when an AI caster uses such a spell and now I have to try to attack the caster to break the concentration, I like that I can do something against the spell. And at least with the talent (at lvl4) that makes you good at concentration, it does not break that easily anymore
But yes, there is much room for improvement and balancing, which does not seem to be possible with the DnD system, because there also seems to be no real "getting stronger while leveling"? At least at lvl4 I do still the same damage/hitchance I did with lvl1. And I have the feeling that even at max level 12, enemies at lvl 4 will still be a threat, but I need to play more to find out
