(Not sure where I put this thread : Gameplay Feedback or Balance Feedback, so meh)
Io is good addition to the realm with unique strategy with pet and interesting mechanics of it (Capping point/payload with Luna, bodyblocks, healing Luna, etc) but I don't think she will be "viable enough"
Good concept, but bad execution, Moji was the victim of it, I don't wanna Io to be the same. Nobody does
So here's some suggestions :
1) 0.5 sec delay on Moonlight when de-activating it feels annoying and teammates can die in that amount of time. Remove it completely (or at least make it 0.25s delay or something) I know you can switch targets during heal but keep in mind : resource doesn't regenerate while healing
2) Travel time is another annoying issue. Again, teammate can die while heal travels. Not sure what to suggest here, maybe make it faster
3) Sacrifice talent is just bad. Io's damage output isn't enough to be damage support but Luna can help you with that. But here's problem : you need to place Luna far away from enemies to escape safely, that means no damaging help from Luna.
How about change that talent with something else like :
1- Luna attacks 50% faster and now teleports to you when below 20% of health but her health is decreased by 1000
(there is a card which can give Luna 1000 health back but requires you to waste 5 points in loadout)
2- Reduce cooldown of stun by 10s (5s stun)
3- Keep Sacrifice's effects but it also modifies your bow/your Rmb in some way
4) Goddess's Blessing is also lacking. Suggestions :
1- Moonlight now heals 50% faster (heal output AND travel time) but also consumes resource 50% faster
2- Moonlight now works as healing beam (straight line kinda like Jenos's ult but smaller, lasts with resoruce, can heal through multiple people)
3- Moonlight now regenerates during use at 50% effectiveness (kinda like Khan's Lian Shield)
Hope that helps
P.s : there's also card Protectors which can stack amount of resource given to you but it's such good card I don't wanna see it change, so please, don't