I have a HUGE pet peeve about balance and people posting obviously overpowered ideas. So, sorry about this but it really grinds my gears.
20 second cooldown? That's a bit extremely low for this game.
Diurn is insane. Sure it'd probably overheal for most of it but if you critted a Ben2 you could essentially ignore the tank for ages.
Noct is also strong.
Diurn is just silly.
Noct makes the last one pointless as they are essentially the same.
Diurn is pointless.
Noct is silly and an obvious "pop this to block sh*t tons of damage for your whole team in all modes"
This is just... Essential Dignity is borderline overpowered as it is now.
Diurn is just ridiculous.
Noct is too.
Noct gives you a free gravity, at no mana cost, every 23 seconds. Groups of enemies would be a joke. Diurn with a 25% AS slow for 6 seconds? A strong defensive tool but outshined by Noct.
Diurn would never use this. Root is trash. Noct version is way better.
The goal seems more along the lines of making AST completely broken overpowered. That, or you just don't understand balance.
Why? To make it even stronger? Being able to sit on charges and popping them when we need them would just be too strong. Especially if each is on a low cooldown. Lightspeed is fine as it is.
Or throw on Ewer and let them spam fires forever. Balance is a HUGE DPS increase and no one would ever use it on a healer. Arrow would just be nuts. Spear makes no sense as it cuts all cooldowns down by 30 seconds, when you have a cooldown on your list that takes 20 seconds. And with Bole you can just slap it on the tank and focus on DPS, sure it only lasts 15 seconds but if timed right you essentially have twice that (or more) of free DPS time, depending on the damage going out and cooldown usage. For just a one minute cooldown these are all way to powerful. This makes AST/AST an insanely powerful combo.
I don't see the point in this other than to just further break the balance of an AST. Ast would be able to everything they need to with this without stepping on the toes of, but pushing out, their co-healer, further making AST/AST strong.