That's fair. Ever since the servers moved nearer to me I've found it smooth as butter (especially before moving onto the GCD), but experiences and preferences will obviously vary.
That's an awesome system. I just got confused by your mention of other combo-based classes. Arguably, they should all act more like that, but since they don't I worried it would just turn into ABCABC spam. Your system easily could end up that way as well if it has too few paths to optimize, but I'd rather not assume the worst. Solid concept.
I never assumed otherwise. I'm just worried by how the damage<->healing recharge system would work in typical content.
I feel like there are obvious reasons why WHM's load-up system (be it StB's GCD->oGCD version or the current GCD->Misery version) basically just reduce the cost of healing rather than limiting damage abilities by healing abilities cast or vice versa.
Depending on the details not listed in your sample (e.g. how many seconds of recharge are skipped per "restock"), it feels like in content that requires low healing you're either going to be (1) limited to spamming Gil Toss (and oGCDs used only on their regular CDs), as per a Glare/Malefic/Broil spam healer already, or (2) obliged to just throw out oGCD heals every other GCD regardless of any healing actually required so you can go Healing-Damage-Healing-Damage-Healing-Damage in an apm-bloated cycle (e.g. Bomb-Potion-Bomb-Potion or HWrath-XPot-HWrath-XPot once you've spread vulnerability and DoTs). The latter would have to feel very lackluster per throw not to be ridiculously overpowered over time.
That's largely why MP initially came to mind, as it'd at least apply some limitation to ability cycling or provide a more granular means of allowing for that cycling. Remember, abilities can have MP costs too. That, not any GCD based "Spells" or weaponskills, is where I'd figure CHM would use MP.
Of course, MP doesn't have to be the solution; it could be anything, but right now your sample seems like it has a glaring hole that, frankly, MP could have easily solved (even if not necessarily in the coolest or most unique manner). At present, the restocking feature seems like it's halfway to something great, but is at present a convolution that doesn't seem to meet the intentions you've stated. Given that you've already added that much complexity, I don't see why you'd be unwilling to tap into a further system to make it actually work, or, if such truly would be overcomplicated, reconsider the restocking system entirely.