An arguement towards having Healing on DPS

[Archwizard]

No, it isn't. RDM is the odd DPS out with self-sustain. No other DPS can heal themselves even close to as well as a RDM can. And your proposed changes are ludicrous, they would turn BLM into a self-healing god, and it would come at a cost!

To be fair, most other DPS really don't need to, given their higher base survivability or greater frequency of survival tools than BLM. In most cases Second Wind and a mix of Bloodbath or CC would be enough.

... You're aware that with only 200 potency unaspected damage you would still prefer even a Fire 1 for damage, right? I'm not worried about being a "self-healing god", particularly if the heal is still weaker than... name any other heal in the game, and can only be used on yourself. The value I gave just isn't godawful like old Drain's "80% of 80 potency".
We're just squishy, so a 300 potency heal is a lot for us.
But yes, in that regard, it would come at an immediate cost in that you're casting Drain instead of casting Fire IV. Again, much as you're losing damage while casting Vercure instead of Jolt.
But considering it's a personal tool that doesn't impact raid value -- and in fact, would ideally never be used in raids except in emergencies, since a real healer would still be more effective, just look at how rarely Vercure gets used for that -- your peak output would not need to be changed, no.

(just as BLM being given a Raise would come at a cost)

1) Raise has a raid value; it intrinsically brings up group damage compared to death. A self-heal on a DPS would not, especially if they're not doing their main rotation while casting it. RDM gets its damage downtuned due to access to spammable insta-Raises that would otherwise cost a healer 8 sec to cast and simultaneously bring up a player that much sooner, not for their passable self-Cures that cost a GCD either way.
Best case scenario in a raid environment, Drain saves the healer having to throw a heal on you so they can throw an attack instead, but which is worth more damage and healing overall: a WHM Glare (300p damage) plus a BLM Drain (200p*1.15 damage, *1.5 healing) as presented, or a WHM Cure (400p healing) plus a BLM Fire IV (300p*1.8*1.15 damage)?
If each job does what they're best at, everyone wins.
Outside of emergencies and niche cases, the only value Drain intrinsically brings up is outside of a raid, much like Sleep, so your BLM's peak damage need not be affected.

2) You're still the only one bringing Raise on BLM up and it's an unflattering look for you.