You guys seem to be forgeting that uproot is not channeling, you can cast and forget it while rook has to get right up on the tower and take hits to deal his damage.
Try maxing uproot damage with compost (which does not require you to get the kills as someone suggested, but merely be near grunts that die) then doing a hit and run strategy. Uproot has longer range than the tower so you can cast it at the beginning of a wave, kill some creeps, cast again, Alt-tab out to read the forums, alt-tab in and cast it again, cap a flag nearby, run up and cast it again, etc, all without taking any damage.
There is absolutely no commitment to uproot and that alone makes the skill worthwhile when comparing it to Rook's Slam/munch combo. It is a shame that UB can deal almost equivalent amounts with spit, but then again he has to get in range to cast so he will take a hit or two maybe.
Or you can just skip doing all that, and just run up to any tower not being defended at about lvl 5+ with minions, and use ground spikes about twice with everything hitting it. If no one comes to stop you go right to the next one, QoT can take down towers extremely fast without 4-5 points in uproot and 3 points in compost.
Right now if you got 4 points in uproot, 3 in compost, 4 in ground spikes, and have a full minion army, and do everything in the proper order, QoT can probably kill a tower in about 2(seriously) seconds at a decent level, and you guys want her to get buffed for siege? this is without any support from creeps.. hell if you got all of that, qot could take down a citadel in about 10 seconds with absolutely no support. But you guys want uproot buffs? Uproot needs to be completely redone or scrapped, not buffed.
btw the 10 second citadel kill, i tested that on a lvl 3 citadel but still, I think my point is made, buffing uproot? When i can kill a tower in less then 2 seconds, uproot doesnt even get through 1/4 of its cast.
So why even have uproot, if you buff it, im just gonna go backdoor towers by the citadel early game, and if your team ever gets killed, I can kill your citadel in in about 1/3 of your death time, thats by myself. So.. yea maybe if you buffed uproot it would be worth getting to get cheap ass wins like that.
OK wow that was a big random rant I went on, anyways @OP, qot doesnt need another way to heal, and the skill idea doesnt make sense with QoT, if anything she'd drain mana from a person by charming them with a channeling spell, or something like that.