One of the nastier side effects of the split general/specialization trees currently is that there's very little incentive to split the few perks gained from levelups over the trees; Realistically your faction leader channeler is likely to end up levels 9-12 by the end of the game unless he's engaged in a lot of combat on a huge map or invest heavily in the XP perks (in which case he also needs to gain significantly more levels to reach the same number of perks invested in anything else than the xp perks), and that's just not enough to invest heavily in both one school of magic and deep enough in the specialization tree to pick up something truly useful or with a good synergy.
Add to that, that most of the schools of magic provide either utility (useful regardless of specialization perks, and the best utility spells are level 1 or 2) or damage (which is low without specialization), while specialization generally provides either good utility or damage, but only if you invest deep in specialization and pick up a high number of filler perks, and we've got the weird current situation where even dedicated channeler mage faction leaders like Procipinee or Magnar are better off skipping their schools of magic except for any extra levels they can gain via soul-eating the champions they recruit and go all-in on their specialization, using lowlevel spells and those opened up by their specialization. (With going all in on the general perks to pick up spellbooks for utility and ignoring mage perks for most of the game a reasonable alternative, though less effective for damage or summoning)
And as for picking up some level 7 or 9 mage-hero with low spell-paths and thematic but poorly-chosen for either damage or utility spell paths... Let's just say that it is a sad day for a game entitled "legendary heroes" where the primary use for the combat heroes when fighting against the AI is to cannibalize them for magic or set them as permanent -5% unrest reducers. (And don't get me started on heroes that, very thematically, have been designed with a split into some non-spellbook general perks and some specialization perks. Yes, it is very thematic, but it makes them so very, very, weak overall.)
One obvious way to address at least some of these issues would be to go to a "pick one general and one specialization" perk per levelup rather than making it a choice between them. That would also allow the placement of a few more general-purpose perks in the general tree with at least some chance that they'll actually be used, and it'll make thematically designed heroes recruited through fame at higher levels much more interesting and useful, as they'll be able to have both a somewhat useful specialization and (if their theme requires it) the magic to back it up. No more "this level 9 mage hero starts out as an apprentice in his art".
Thinking off the top of my head, some obvious examples for adding perks in the general tree if this idea was even partially followed:
Anti-Swarm I->Anti-Swarm II -> Anti-Swarm III (Counts n fewer stacks for being swarmed. In effect, Anti-Swarm III makes it nearly impossible to be swarmed if the hero is part of a defensive line, while II is enough if the hero is in the centre of an anchored line and only attacked from either front or rear - point being, the player will notice a significant different regardless of investment level... I realize this is impinging on defender territory, but really, swarming and heroes as currently implemented is devastating to heroes. The defender "immune to swarm" could profitably be changed to "the hero and adjacent friendly units have swarming damage halved" in that case (or the even wider "army takes half swarming damage")
Strength (+2 attack) -> Adventurer's Boon (+8 hp) -> Adventurer's Grace (+25 fire, cold, lightning, poison, and spell resistance)
Tinker (extra accessory) -> Tailor (+10% defense) -> Soldier (+10% attack)