According to various old forum posts, [Healing Return] will not heal [Helios], but the Wiki says it works and I'm pretty sure I've seen it myself, but I generally trust the wiki more than myself. To the point, this gives [Helios] a very direct way of healing that beats out [Djinn]'s slow immortality and ensures it won't be wasting [Primed Regen] as quickly.
[Condition Overload] won't work if the enemy dies on the same attack that inflicts a status effect. That's not really a problem, though; if the enemy is tough enough not to die on the first shot, you've got a pretty good chance that said shot will proc an effect, and you only need to worry about that if the enemy doesn't already have a status effect. At high level play, especially if you're not solo'ing, it's a safe bet that the enemy will already have a status or three on it. It's entirely valid to simply use the normal elemental mods for extra damage and less status chance; depending on your play style, it may very well not make much of a difference in how often [Condition Overload] procs.