I think, his 'complain' is, that is gives no kind of reward/incentive to invest heavily only into a few skill trees. Leveling skill trees beyong the point where you need it for skills feels dissatisfying with exception of Summoner.
In DOS1 maxing a skill tree gave you more master skills and 1 special trait like stun immunity for Aerothurg. Even though not all of those mastery traits were sadly worthwhile. The typical inconsistence of DOS games I suppose. A few good ideas and a lot of idealess filling. Like we see it with racial skills in DOS2:
very special: elf -> new (flesh sacrifice, flesh eating)
special: undead -> new (play dead)
not so special: human, lizard, dwarf -> just got normal skills from the first game