HoT: Healing over Time
One could argue that Soraka somewhat does this, but we don't have a support that purely heals people over time. All 2nd party healing is burst healing.
Any opinions about this?
A long time ago Morello wrote a post about this concept and I think he brought up some significant points.
The main gist of it was that HoT is the most boring and degenerative form of a mechanic that is already prone to being toxic and degenerative to the game (healing in general).
Healing un-does damage to keep champions healthy, meaning that it undos mistakes and invalidates decisions based on enemy zones of threats because enough healing can simply reduce a threat to zero. Burst healing on a long cooldown has a lot of decision making involved as you have to decide who you save and when to save them; Putting some extra health on your Sion is nice, but what if a diver jumps on your adc? the same amount of health on your adc could easily make the difference between winning and losing the game. Even if you use your heal to undo some damage then having that heal on cooldown still means you suffered some kind of cost to fix that issue, this is why Riot has always felt good about the design of Soraka's ult.
To contrast, Healing over Time isn't capable of saving a target in a key moment so you just want to spam it on targets who have lost health to make sure you get the full healing duration and maximize healing output. There's very little decision making or strategy and you just kind of make your team slightly better by existing. They were only OK with giving Soraka significant healing over time (her W being on a low cooldown in the late game makes it more similar to a HoT effect than a long cooldown burst heal) because she has that big health cost that still makes it difficult for her to spam her healing and makes it so Soraka taking damage from enemies shuts her down hard.
Janna doesn't really do healing over time. She has a sustained, channeled heal. I would absolutely love to see some legitimate healing over time. Works really well in HotS and is something that would bring some variety to the healers in League.
sona could start stripping a little bit to make the bot lane a bit more hot
Except Janna does.
if 
hits a q then uses w on an ally she actually does Heal over Time.
Taric kinda does HoT if hes allowed to autoattack
I would love to have that kind of heal in the game.Closest to it is Janna's R and Soraka had something similar to it (after her rework,but it was removed if I recall correctly)
Soraka does with her Q+Heal
heal over time is useless. people die too fast.
Why would you even want that ? If there was such a support the other ''burst healers'' would be picked over it. Playing 
has the same effect but better tbh
technically 
used to increase nearby allied health regen in s3 and s4 I believe, this was the largest healing at the time next to the burst healing from supports. I also do believe that a champion focused around an alternative healing method kinda how bard works (he uses indirect healing with his shrines) would work well if there was a need or reason to have one, perhaps a support that had a zone effect on a toggle with an immediate heal followed by a passive heal for a set number of seconds EX: 
casts W which heals for its normal amount then for the next say 5 seconds the target ally heals for 50% of that first amount again. it wouldn't negate the damage but it would leave the decision to engage up to the person being healed, (do I engage while I'm regenerating or do I wait till my extra healing wear off?).
Another option is to make an item that alters healing effects so that they perform healing over time because its easier to say an item is overpowered and fix it rather than designing a brand new champ or changing an ability then saying well you know we messed up we gotta go back to before.
I don't think it's a degenerative mechanic - I asked the same question about 3 years ago.
It was an era when that sort of thing wasn't overpowered, back when tanks were stronger than just their CC and bruisers were a real thing (they're not anymore). You could heal them with HoT's in a teamfight indefinitely, sure, or for a long while at least, but they wouldn't be enough to keep your marksmen alive as keeping marksmen alive was a matter of positioning over everything else.
Now you almost want your marksman on the frontline so they can do more damage more quickly. It's literally all about them now.
Not to say that hasn't been a thing before; protect the Kog/Trist has been a thing since basically the beginning. But to this degree, and for every single marksman, is pretty absurd.
RIP old shen Q, 'twas my favourite ability. 
@thread Passive AoE heals based on AP a la Lucio.
You could have a kit thats designed around a passive, AoE field that, on a toggle, either heals or shields. The ramping shield could do... lets say 20% max health over 10 seconds, and be refreshable. The heal over time could do 0.25% max HP, 0.25% missing HP+0.15AP) per quarter second.
The rest of the kit could be mobility and CC; One ability could be increased movement speed while near allies, increasing the more allies there are. One ability could be a knock back/root depending on if you have your heal or shield active. And the ultimate could double the effectiveness of all your other abilities; Your passive would become 40% over 5 seconds and 0.5% +0.3, your movement speed would become ludicrous speed, And your CC duration could be increased.
Soraka's Original Heal was actually a Heal over time. That was WAYYYY Back in the day.
HoT has no place in an MMO like League where the main healing counter (GW) does an extremely good job of shutting it down with little counterplay. Even without the existence of GW, a HoT would end up being more than likely broken. Since by nature, it needs to be either spammable or really high in base value in order to break even with burst healing. And all this would promote is brainless and passive heal spam.
Besides we already have Soraka and to some extent Janna.
It would be interesting, but it'd have to be managed a lot to make sure it didn't become a toxic, boring mechanic. Maybe something like a Swain ult for an ally?
None of them do hot?
