Issue 1. All “shield bash” attacks are not affected by the “up to 5 targets per hit” limitation for the purposes of Heal on Hit and Heal on Stagger talents
By “Shield bash attacks” I mean: the first charged attack of Flaming Sword, Flaming Dagger, Axe and Shield, Sword and Shield; the second charged attack of Mace and Shield, Hammer and Shield.
With all other attacks, Heal on Hit and Heal on Stagger talents are capped at 5 targets per hit. If you hit more than 5 targets, you get healed as if you only hit 5 targets. With any shield bash attack, you get healed for each target you hit, no matter how many. So if I stack 50 enemies in the same spot and hit them with a shield bash, I get healed for 50 HP with Heal on Hit talent or 100 HP with Heal on Stagger talent.
Issue 2. When hitting multiple targets with Flaming Flail’s first charged attack, both Heal on Hit and Heal on Stagger talents work as if only one target was hit
Flaming Flail’s first charged attack has a similar area of effect to shield bash attacks, but its interaction with healing talents is totally different: no matter how many targets I hit, I only get healed for 1 HP with Heal on Hit talent or 2 HP with Heal on Stagger talent.
All of the above was tested on modded realm as a host, with Enemy AI set to off. Limited testing in normal play seems to produce the same results.