it seems like regenerate might be good if you know your about to start a fight soon. where as heal is the shoot! the tank just dropped to 0 and i need to get him back up now type spell.
Spot on.
Regenerate can be awesome if you have time to prepare, and you are fairly certain the enemies will attack the character with regenerate. Ie fighting hoards of creatures, dumb creatures, or if you have a choke point.
On the other hand, it is a bit cheesy to play whack a mole like that so your millage may vary, I know a lot of DM's house rule that bad things happen to you on 0hp to get around this side effect of 5e.
I've also used regenerate out of combat on NPCs quite a bit. There's always a wounded NPC missing a leg or an eye or something who you need something from, and regenerate works a treat in getting them on your side.