The devs have said in the past that they don't mind those OP builds but they should be harder to achieve AKA it's likely they will be enabled via hard to find gear and/or synergies. i.e;
Wizard 3-piece set bonus;
-Every enemy that is killed in Archon form adds 1 second to the duration of Archon.
Barbarian Legendary Weapon Affix;
-Every 25 Fury gained while Wrath of the Berserker is active adds 1 second to the duration of the effect.