I use Arcane Enigma as an 'escape option' and almost never a a direct attack so I decided to swap out for Arcane Lotus to see how it compared since I wouldn't miss the damage option.
I've run through a few games of Turf Takeover and I'm pretty sure I'm switching back.
As outlined by others, there is a movement penalty and it does last for a shorter period of time, so as an escape option it's inferior to useless despite the fact that you remain invulnerable; you simply can't cover enough ground to get behind cover and out of harms way.
As a healing option, it has no effect on your own Health and unlike a Sunflower you can't tell which of your teammates is in need of healing unless you were standing there at the time watching them get hit so while it does Heal +4 over the Sunflower Heal Beam's +2 it's short duration only makes it good in a pinch, and only if your teammates are right around you.
If it provided self-healing it'd actually be useful but as it stands any healing benefit is situationally limited and minor, it offers less time being invulnerable as an escape option and it slows you down which further hampers your ability to remove yourself from harms way- I'll continue to use Arcane Enigma.