These won't address the principle components that make her gameplay unhealthy. She has horrible roaming and fairly binary matchups, making life hell for melee opponents but being worthless against any character with range.
The DoT change I agree with for the opposite reason- High damage dealers with sizable cooldowns, like tanks with slow autos and %health damage, can't break the spirit minigame nearly as well as they should. Make the spirit timer tick down based on damage dealt, not number of attacks.
Decrease the tentacle spawn timer to let her roam and set up further reaching gardens, and add a timer that prevents them from regrowing at the same spot immediately, to let melees that have a hard time getting close enough to them actually be rewarded for thwacking them during the laning phase. (15 seconds, decreased by 5 seconds for every rank of R).
Have E deal some raw damage to minions or monsters it hits, causing tentacles in range to slam over the area. The idea being that the test of spirit automatically determines beings without spirits fail the test immediately.
Have W's base %health damage increased by 1 at rank 1 and by .5 each extra rank (3/3.5/4/4.5/5% health -> 4/5/6/7/8% health). This is to compensate for the tank update shifting tank items from granting health to granting resistances. 
got a similar change to compensate recently, going from 7 (14) to 8 (16) % health damage on her Q (with both hits). Maybe lower the scaling %health damage go from 2% per 100 AD to 1.5% per 100 AD since the higher base damage would let her build a bit tankier without giving up much damage.
She'd probably need a little more to make laning against her better for melee opponents, but the damage-based spirit release and tentacles not respawning right away might be enough additional counterplay, and the faster ordinary tentacle spawn rate would let her do much more in team fights, where she is currently abysmal.
