Yes, every single one only heals up to 6. Master restoration staff only restores stamina to 6 targets as well. Healing springs targets per tick, solidifying it as still the best AoE heal since it can heal different targets each tick. The only uncapped heal I know of is healing orbs which hit for 1.5-3k per tick but I don't use these because you can't place target them and a lot of times by the time they reach someone who needs a heal from them, they've already been healed. Use quick siphon.