Hell, you really don't even need quelling. The dude already has 80 damage straight out the gate. That's twice as much as some carries have to deal with. Spend the cash on a shield instead, and just laugh at enemy harassment as you sit in the wave and deny everything. Grab a little cash when the carry ain't looking, build yourself a soul ring and have a nuke-slow-heal on demand for the rest of the game.
Treant is fantastic. Even later in the game he has his uses, since the damage block will stay relevant for a very long time and having a 4.5 second area root (on a 70 second cooldown, no less) that prevents autoattacking will stay relevant for a LONG time... And all throughout, he's punching things like a truck and being the bane of jungle farmers everywhere due to his ability to invis around the whole damned area, WHILE using stuff like Leech Seed, orchid, dagon, necro, or any other activatable item you decide would be fun to be able to use while staying invisible.
The dude can actually semicarry to a small extent if given the right farm/items, if only because of his absurd base damage and massive strength gain. ...you'd really need farm for this though, and you have better things to do, generally. Like being awesome.