Will516,
I disagree, the shamblers scale extreeemely well. Especially with Entourage AND Compost. With both those skills maxed the shamblers are about twice as powerful as any other summonable in the game. That's just raw numbers, it doesn't include the splash damage they do. So in true DPS they are 250-300% stronger than any other minion.
The trick is to keep her alive. I've looked at some different wasy to distribute her skills. If you're going to max shamblers, entourage, and compost... you can either go for the Bramble shield/groundspike combo and use shield for survivability. OR, you can go mulch and morale.
If you're going mulch/morale, Spike Wave may also be useful. You can take points away from morale and put it in spikewave if you choose. I like spikewave, so i usually do this.
Shield is a better defensive spell of course, but if you're pushing mulch/morale you'll probably get priests as well, so it balances out.
If you're going to leave shamblers behind, you'll want to take Shield/Ground Spike and Spike Wave. These are fine support spells. And you have two options for your damage.
Either pump Morale and use Idol Minions. OR, go Uproot and Compost. Uproot will be your primary damage out put for the game, so it depends on the gametype.
Uproot is not super impressive on it's own... but if gets Quite nasty with maxed out Compost. 3000+ Damage to Buildlings (+splash damage later), for a ~900 mana instacast on a 15 second cool down. Get some hats and cast as often as possible. For reference: Towers have 5600 HP, in Fortress mode, fortresses have 15000. Basically, she can single-handedly drop a fortress if she gets two solid runs at it.
QoT is the master (mistress?) of raw damage output. But she's fragile, she'll need either bramble shield or mulch+priests to stay on the field.
Compost is NOT optional if you are using the abilities it supports.