I would say that the towers hp upped, damage down slightly, so that they arent just pointless to build. If the HP is to low, then they might as well not be there at all when the game gets to higher levels. Which would result in a, "Why even put the time into building the skill", thought.
I like the idea of getting xp and gold for what they kill. I think it should be that way with any minion.
I think though, that the as far as the towers go, they need to be able to be placed down a bit quicker. if your putting 6 towers down, you have to be standing there for nearly a minute to do so. Thats a lot of time in combat, for a minion that doesnt follow an enemy, nor hit hit as often. Oak for instance can summon all kinds of ghosts and have them pouncing on you as he wails away. It makes the rooke somewhat weaker than his counterparts.