Uh... o.O (I'm not thinking of any kind of innuendo, I'm just not sure what "wet slaps" in this context would be... like what kind of medical instrument or device makes "wet slaps"...?)
That said, yeah, Miyuri is one sick dude.
No. It's not like that in any way. But nice try.
More?
Okay: In order to make it where it's worth using - to the people that say it's bad - they'd have to make the potency really high. Then it couldn't be a channeled ability. If the potency is less than the GCD of Glare for a tick, it's bad to use. This means an ability that ramps up OR an ability that starts high and ramps down (people would just cancel it at the point the down-slope crossed the Glare damage line). That is, if you had an ability that started at 500 potency per sec and decreased every by 50 potency every second for 10 seconds, you'd terminate it early since the last bit would be lower damage than a Glare. On the other hand, if it ramped up, the end point would have to be really high to justify the risk of ending it early. Conversely, if it was level the entire time, every tick would have to have a normalized damage greater than Glare as well. In any other case, it just makes more sense to cast a Glare. And it has to be higher ENOUGH to justify the risk.
That is, if you make it do greater enough damage than Glare, it still has to be significant otherwise you'll say it's not worth the risk. So for example, 310 potency for a 2.5 sec GCD (Glare III) equates to 124 potency per second. This means that if the channeled spell did, say, 125 potency per 1 second (312.5), you'd appraise it as not worth using (the locked in place risk) over Glare or that it's not "rewarding" good use/the risk involved. But at the point where it DOES become a solid increase, it's now likely great enough to widen the gap between the floor and ceiling player wider than the Devs want.
"designing it as an intuitive, rewarding ability commensurate with the added risks", in other words. (Not to mention "intuitive" and "rewarding" are not precisely defined terms here...Misery is intuitive and rewarding to most people, but you seem not to agree.)
One thing I think COULD help is if a channeled ability was your main nuke spell. Like, if it was your go-to "spamnuke" and had no CD on it. Most channeled abilties in MMOs tend to have some CD. The closest ones to not that I can think of are some iterations of Arcane Missiles on WoW Arcane Mage had low recast or procs or something so they were up all the time, and Shadow Priest Mind Flay. But in this case, it IS your spam nuke, and you'd use a different ability instead when you needed to be more mobile. So take SCH, for example. Imagine Broil IV itself was the channeled damage attack. Something like deals 120 damage per second for 3 seconds, 3 sec GCD. Note this normalizes to 300 damage per 2.5 sec, so this is doing more damage than current Broil IV. Then you have Ruin 2 over here on the side as instant cast that does 220 damage. In this sense, Broil IV is the one you're trying to use every 3 seconds as your channeled ability nuke and Ruin 2 is the button you press when you need movement, since it does more damage than Broil IV for anything less than 1.83... seconds of channel. Granted, you might normalize it over 5 sec or something instead, but whatever. So maybe Broil IV would be "120 damage every second for 5 seconds, GCD 5 seconds, channeled, consumes 150 MP per second, action ends on movement".
Point is, it can work that way, but then you'd probably dislike it since it would be swapping one "spamnuke" for another. Though arguably a much higher skill level other - Ruin 2 would now HAVE to be used (other than Biolysis natural refreshes) for oGCD weaving, for example, and you'd be pressing half as many Broil IVs because each would last twice as long.
That said, it would raise the skill ceiling some... even for good players who know where to plant their feet, oGCD optimizing would become tighter. You'd want to maximize every Ruin 2 cast by finding times where you need two oGCDs, like burn an Energy Drain and then pre-cast a Whispering Dawn for damage happening in several seconds using the Ruin 2 window to move to the safe spot and then hard channeling Broil IV once you get there.
This.
The only traditional sense channeled abilities in the game are, I believe, Passage of Arms, Collective Unconscious, and Flamethrower. Especially Flamethrower because it has some special code where the damage is applied every 1 sec instead of every ~3 sec server tick. I'm not sure how it's unique in that way, but it seems to be. Oh, and Aetherpact is channeled, I guess...by Eos, though, not by the SCH.
I think it may be due to a lot of people thinking of Blood Mage for that. Not in the WoW (lore) sense for Blood Elves, but in the sense of Vanguard, Saga of Heroes. Apparently they had a class that worked as a sort of vampire healer, stealing health (damaging) enemies in various ways and spreading it as heals to either the mage or to their defensive target or party. People don't tend to think of that as Necromancer because it's not a Necromancer in the normal sense (no raising of undead thralls as minions and such, Raise aside).
Or imagine a WoW Warlock that did less damage but the health drain abilities it had healed party members as well as themselves. Something like that, anyway.
The problem is, FFXIV's combat system is, yet again, too rigid for this to really work. They'd just be regular heals with or Kardia that just had a different aesthetic. If SGE was renamed Blood Mage and Dosis to Drain Life, but worked exactly as it does today, one could argue it was a Blood Mage/vampire healer. But it would mechanically be the same thing.
I think that's fair. It's not for everyone, but I honestly enjoy it. Which is weird because I prefer healing to doing damage, but I think it's because I like the aesthetics and I like how it is brimming with oGCDs so I feel like I'm able to engage with them all the time (unlike SCH where I feel I have to use my AF on ED and am limited only to longer oGCDs). I like being able to actively and continuously shield allies with Karachole, which no other healer can do aside from SCH, and SCHs that do it are "bad" (using AF on Soil instead of ED). It is funny that the "heals by doing damage" healer appeals the most (in this group of us) to the person that likes doing damage the least. Funny how that worked out...
Agreed with it needing to be the core of the rotation, though, as I said above myself. Tranquility is one of my favorite buttons in MMO history. Did they make it where it's not just your party? I think it was originally raidwide, then they nerfed it to just be your party, which was lame.