In a fight that i know my mp will going down fast (susano ex for example), i have several way to maintain my mp as ast.
- always keep mp card on spread, use it when your mp drop to near 1/2, even better with Potency or duration royal road
- lucid dreaming obviously
- lightspeed, if you think you want to use it, do it. Ast lvl 68 trait give us more leeway on using lightspeed
- largesse can act as mp buffer of sort since bigger heal mean less casting mean less mp
- try not to spam aspected benefic/helios, this spell is one of the reason why ast mp going down so fast now
- dont spam combat spell, dot spell like combust is fine but not malefic and obviously gravity, in a fight where everyone can go from full hp to 1/4 hp in seconds, dont risk it. Remember you are healer.
- i know this sound awful but if 1 dps die, dont just rush swiftcast + res immediately, make sure your mp is enough and everyone else is top off first.