P.S.: Srsly, if someone uses the +15% heal tactic of the knight to increase his selfheal when running around solo...

Additionately (iirc) the +15% heal worked on the mythic servers only, if the groupmates were in 30 feet range around the knight, not 100 feet like the description may suggest. Maybe someone can confirm/deny.
Also: WAR is designed around a modified "rock/paper/scissor" balance and in a real RPS balance you wouldn't see any selfheal on tanks at all. If anything, selfheal on tanks should be rather nerfed than buffed.