I have a list of suggestions I think would better the gameplay as it stands.

Oak:

-Spirits should have decreased damage as they travel farther from Oak, as well as having lower base damage or lower HP to begin with (or a combination of both)

-Give Oak's banner a slight health/mana regen aura as well as armor aura making it useful out of combat (like +3/+3 last level)

-Oak's morale could be changed to give AoE resistance to spirits (against towers, TB, etc) so they can't be blown to pieces as a group, drop the life add.

-Summary: Other than that I think Oak is a hell of a fun time to play, I just avoid touching him because of the stigma of OP spirits.

Rook:

-I love the ground target hammer slam, but I wish the minimum range was a bit closer to the Rook. Also there is a bug where if you click outside the minimum area and he turns around to face that direction he will do a U shaped turn movement such that the targeted point is within his minimumrange and he will start 'dancing' back and forth instead of using his hammer.

-A little more damage build up with multiple chained towers on the ground would be awesome (lower damage with less, more damage with more.. basically steepen the curve so that 8 towers becomes a real challenge to tank but 1 tower isn't a huge issue)

-Add passive effects to Structural Transfer and/or God Strength to benefit Power of the Tower. For example: 1s/2s cooldown reduction, AoE damage, +life, +dmg, etc. With synergy bonuses like that there would be good incentive to play a full tower/wall spec Rook whos only direct attack ability would be boulder roll as getting high ranks of Hammer slam would be difficult.

-Stat booster should affect his planted towers in some fashion.

-Summary: Rook is fun, but he seems like a one trick pony as far as builds go.. Hammer Slam, Boulder Roll, God Strength <insert ability here> (I do the stat booster, or maybe towers).

Unclean Beast:

-Make Beastial Wrath +dmg and +attack speed, but balance the dps increase to the same amount as it is now, Beastial Wrath will then allow application of proc items more often name Mage Slayer late game.

-Stat booster ability should add life leech, that is the seelling point of the UB right?

Regulus:

-Spread the mines out a bit or lower their damage.

-His stat booster ability could add movement speed (for those strictly auto attack builds)

I'd like to see more places to dump skill points into, whether it be new passive effects or active ones. Having one more active ability per Demigod would be awesome, it wouldn't even require allowing 5 active buttons... there could be a "branch" type mechanism where you choose one ability or the other and the other is restricted (maybe for Regulus:  Snipe OR a new poisoned arrow ability with some side effect).

Thanks for reading,

TLDR:  Rook needs power of the tower viability, for the love of god nerf Oak, overall we need more variety in builds.