First glance, I thought I might like this champion.
I really like your approach to the theme and I think it's a really fun idea, but the skill set is pretty much a mix-and-match of other pre-existing skills with no new ideas.
I like how you tried to tie in a passive to her other skills. The idea is a bit clunky with the way you have it work but it gives your champion that bit of uniqueness that I like to see. The only problem is that this puts reliance on farming minions in order to perform optimally.
Q - it works, but it's pretty generic.
W - decent slow with spice and some damage, but utility will depend on the range of the skill.
E - can be used for zoning or buffing allies, alright. balance depends on size, duration, and damage of the cloud. With regards to the stun, Viktor's AoE stun only takes 1.5 seconds to stun whereas yours takes 3. His also slows so that enemies have a harder time running away, but yours only deals damage. As far as the buff goes, why force your allies to stay inside in order to get the full heal? Speed buff is pretty similar to Orianna's W.
R - Buffing damage on your team and increasing damage taken by enemies is pretty much the same thing, and is very one-dimensional and stale. Try to mix up the buffs/debuffs.
Her skillset doesn't lend itself to tanking at all. If you wanted her to be something like Alistar as far as tanky/support goes, remember that you need to have hard cc and durability in your skillset. Right now, you are going for damage with a little utility and added damage with more spice. Things just aren't fitting together for a clear role. It's leaning towards melee support without the control that a melee support brings. Leona/Alistar have lots of hard cc and mobility with less on the buff support side. They focus more on control and survival than on adding to your damage. Not to mention that you need spice in order to get your control. Again, this all depends on the specifics of your E. but she's still lacking a tanky steroid that melee supports usually have
I like your theme but hate the skills as far as innovation goes. It works to an extent but it just seems meh gameplay-wise