The engineer mortar elite skill nr.3 (launch elixir) heals in an aoe but doesnt scale with healing power as the gw2 wiki entry suggests – therefore i assume its a bug which was correctly implemented at some point.
Gw2 wiki link:
http://wiki.guildwars2.com/wiki/Launch_Elixir
Tested in heart of the mists vs svanir/chieftain using clerics and berserker amulett both result in 370 healing