But if you don't stay, then what's the point in getting their favor? They're staying in the grove, they're not going to be of any use to you beyond the grove and you're not going to be of any use to them since they already have the thing they want. Aiding them gains you the favor of a group that's sealed themselves away and isn't interested in interacting with the outside world anymore. Though fair enough, they could offer to give us insight on our tadpoles to get rid of us. But helping us against the absolute? I don't think for a second they'd do that since again, their whole thing is isolating the grove and themselves.
Also, I feel like Kagha does offer to pay us. Am I remembering wrong?
The Shadow Druids are a pretty large group. Getting their favor would mean getting a pretty large and powerful group in our corner-pretty handy against the absolute. Just like the non-shadow druids can help us, there's no reason the shadow druids couldn't give similar support, and there's no reason why our need to leave the grove to continue on towards the tower and the desire of the shadow druids in the grove to stay behind. They could give their insight/quest rewards/etc and/or send kahga or whoever to tag along in place of Halsin. Alternatively, if we do their dirty work for them, the rite is unnecessary, since their goal was to isolate the grove so they could weed out the druids that didn't see ideologically eye-to-eye with.
And unless something's changed or my memory is failing me, Kahga doesn't give you jack. You kill Zevlor and the quest basically hits a brick wall and she basically shrugs it off.
