I like using Comet Fall sans damage-boosting-metamagics for crowd control as well as the other spells you mentioned. Good option for when mobs are immune to Greater Command, and it has a shorter cool down than Celestial Bombardment.
Hey there, thanks for your comment
Cometfall is a great spell
. I tend to use it from the time it first becomes available (around lvl 12 for a FvS) until close to endgame. For my build specifically, it falls out of use a bit at endgame because it's Conjuration-based (and Reflex save, which tends to get saved more often).
Being a healer first and foremost (both by choice and by design) limits how many things I can successfully do simultaneously. Since I personally go for insta-kills as a secondary aim (i.e. in between heals, if/when time allows), I can just about stretch my secondary focus to necromancy and evocation (Implosion) working successfully. Since evocation also boosts damage-dealing spells, nuking ends up being an additional secondary aim as well.
FvS has a limited number of spells per level, so I go with Blade Barrier (evocation) instead of Cometfall at level 6, to synergise with the spell DC schools I invest on.
CC is a tertiary stretch, and normally an 'extra' from spells I cast for other reasons (e.g. Celestial Bombardment for nuking, also does some CC). Enchantment, being will-save based (i.e. tends to land more often than Fort and reflex), seemed a worthy extra stretch for the build, despite the very limited number of spells of that school.
Conjuration, overall, is a bit too far a stretch for this build to make Cometfall worth casting. This would likely be different on a purely nuking/CC build (no heals), for instance, where there would potentially be more room to invest more broadly on spell DCs.