Iz noz hidin' if dem waats fer da waaagh toz weer oft bofors dem com bak. Ifin ones a me boyz gives me a waagh! I givz it right bak! Mor boyz in a waaagh! iz a WAAAGH!
<Translated: If an ork gets a kill and has a 'waagh' finisher that allows nearby orks to 'waagh' respond, then a 'waagh' bonus (which stacks) cannot be exploited by enemies waiting to re-engage after the buff wears off. I would say you keep the waaagh buff until you die and then it resets (perhaps with the intro of madboyz they can 'store up' waaagh and give it out as a buff. If the range of the waaagh response is limited then orks will need to stay close to get/give the waaagh kill/response. :
Imagine your ork gets a kill and that unlocks your 'waaagh' key, you click the 'waaagh' key (triggering an emote) and any ork in range would have their 'waaagh' key unlocked and if they push it the 'waaagh' (with an emote). That allows for the building buff but players that are in the middle of something (aiming/sniping, driving a buggy etc. might not be able to 'waaagh' without getting interrupted by having their toon doing the emote. The more 'waaagh' the bigger the buff, that's the orky way. imho.