When the support becomes the damage dealer :). The guaranteed hits with Medusa goth are quite useful for consistently proccing on hit effects, leading to hutao goth gaming. Allows for quite a decent run considering I am using rag tag bad equipment. 
I will note, I feel there is some issue going on with Hutao Goth where the regen energy on hit effect of the weapon seems to be affected far more than I expected. I find it doesn't give as much when I launch the game, but after playing a bit something seems to change and hutao starts being able to max her ult with her ult against like 2-4 enemies and starts ult spamming which led to the above display. I assume something in the code is going awry(maybe has to do with the 20% chance to deal 50% additional damage as I did use that set) as Hutao was popping far more hits than should be normal with ultimate leading to mass debuffs and huge energy regen.
On another note, at some point having medusa goth on the team disabled favonius set for whatever reason. This fixed itself but not sure why this occurred.
I assume Hu Tao also has Arcane Funnel or Ever Burning Ember trinket equipped? Just having that sword shouldn't be enough to chain ults.
But yeah, I'll have to do a balance pass on these mana-related items. :)
As for disabled set, maybe the damage was too low or there were a lot of misses? If it fixed itself, it probably was something conditional...
Before, I wasn’t using trinkets on hu tao, and after trinkets it isn’t that much different oddly enough. It just seems at some point the number of hits increases permanently(until I close the game) and it starts popping off. So far I don’t find the mana items too problematic(but my gear is poor, I imagine the mana regen on hit one could be exploitable with the right stats), I would imagine a change to make it one per aoe cast instead of on damage basis though to prevent this sort of thing from happening as it certainly is a bit silly to have a whole party of supports as hutao provides the defensive and offensive utility.
the medusa one is just weird as removing her and having a 3 man kept the favonius set working on my existing characters. But adding back disabled it. Thought it was a hidden passive or something until it just fixed itself.
on a side note, does speed affect cooldowns? Like if a skill pops every 5 seconds, does it speed it up? And also does speed affect mp regen?
No, speed doesn't affect cooldowns, only skill LVL in most cases does.
Are you playing on the phone?
Edit: Yep, you are right.
>It just seems at some point the number of hits increases permanently(until I close the game)
Turns out, Navy set 2x bonus stacks until restart. That's why you get all those hits. :^)