Spoiler
I think you mean "since I already have healing and HERBALISM I save the actual slaying of Keethrax for later"

I agree with this, gardening is useless and if you already got frost bolt well then you really don't need it.

Remember that you can even enter DD:7 and GENERATE Keethrax without generating the Artifact Torc (it's generated on his death). If you do this then there are no negatives to waiting to kill him, and several more positive effects:
Easier to kill him due to higher level and more spells. (Less stat-drain, less RIP-risk)
Easier to avoid the cats which usually get generated on the level due to more spells (scare monster, slow monster, teleport (use on the cat), calm monster, stun ray, web).
Probably you'll have access to firebolt or fireball-spell, so you can easily cook the druid corpse and take it to the village druid for a certain potion. Also you should have holy water so you can bless it if it starts to rot.

If you have food preservation:
Higher chance (due to higher FP skill) to generate a giant slug corpse (Acid immunity)
Higher chance to be able to take the (cooked) druid corpse home.

Edit: Just noticed you played a Paladin, which doesn't get herbalism. You should get this skill if you can, and not the book/wand. Herbalism gives you direct access to blessed herbs without spending holy water (stomofillia and spenseweed are must better blessed), gives you status of herb bushes so you can avoid over-harvesting, saves you using uncursing scrolls on e.g moss of mareillon, gives you faster harvesting due to bushes not fading so fast, and makes unwanted herbs sell for more money. If I found a patch of herbs early I would do Keethrax quest pretty fast to get maxiumum benefit.