I think the theory on this one is weird. It seems like it would kill a lot clutch counterplay moves where a low health hero can survive through a killing play against the opponents instead of running away, because a lot of gameplay options are just completely shut down to you if you have to play around accidentally killing yourself with a burst dmg ability. Geist's whole thing is being low health all the time, so... what, she just can't use abilities anymore?
On the flip side there are so many low dmg and DOT spirit sources that in a teamfight it'd be super hard to hit hit this for a counter and not have it negated by something other than what you intended. Seems like it's for a specific 1v1 scenario, because that's really the only chance you'd have to use it effectively, and even then, a decay or toxic bullets on you would nullify it, otherwise it'd need to trigger like mystic burst, at a spirit dmg received threshold.
That's why I think it could work best if it's tied to the parry cool down and animation, with some additional visuals to show it'll bounce spells too. If you miss it, you're stunning yourself for a second, and it has a short wind-up. It would definitely still be a good item against geist, but her ult has such a short cast time that I think it'd only be a good counter to her bomb. Like a parry, it could reflect everything for a short time, so you don't have to worry about small ticks.
The counterplay argument already applies to parrying with melee, and I think in this case it could add a lot of depth to spirit fights.
Right now, IMO getting chased down by a gun hero is much more fun than a spirit hero because of how much more you can play around their attacks. Hiding around corners, veils, parrying, and jumping are all going to make a gun/melee hero work harder, but usually spirit abilities are much more reliable. There's already Metal Skin and Reflecting Bullets, and I think those items are in a great spot balance wise, I'd love to see similar options for spirit abilities.
It might be more balanced as an ability like Lotus Orb from DotA, where it reflects a copy the spell's damage, but does not stop the original instance, just reduces some damage. Then Geist's ult would be cancelled out instead of killing her, reflecting a big lash stomp or bebop bomb could help win a fight, but it won't be completely shutting these characters out.
The niche I want this to fill is giving a way to outplay simple spirit nuke abilities. My least favorite part of the game right now is going up against those big bebop/lash nukes, knowing what they're going to try and do, and not having ways to deal with it. Nukes like Talon's don't bug me, because it's something you can try and juke or bait out. But some of the big ones hit you even if you see them coming, and it doesn't feel very interactive, especially now, with Ethereal Shift being moved to 6k.
But yeah, I wouldn't want this to be a "buy this item to always kill geist", I want this to be a "buy this to engage bebop in a battle of wits" type of item.
None of the recent nerfs have been anywhere near enough to keep infuser and it's greatest abusers from running people down with just one item. Infuser is still an S tier, and anybody who can abuse it really well is still going to be very good as a result.
I'm terrible at this game, so I might be wrong. But I'd think that since this upgrade would be a Vitality item, it would be harder to slot in for a lot of heroes. And it would lose the original Infuser active, so I don't think many heroes would be interested in the upgrade. It would be like Kinetic Dash / Arcane Surge, which fill slightly different niches, and both get used on a variety of heroes.
Do you think this type of item could be fine if it didn't build out of infuser?