I disagree with this. You don't need 5K haste at all. I'm rolling 36.18% crit fully buffed (flasked + fed as well), yet only 13.78% Haste fully buffed (1.98s Fireball), it's not hindering me greatly.
http://www.worldoflogs.com/reports/rt-2sx307r128bkgrg6/
I did Durumu and Primordius with currently Armory; beforehand was 502 iLvl with T14 2 set and some crit off-pieces. Screwed up majorly on Council; ended up dying due to being bad and didn't even have a flask on it, Megaera/Ji-Kun was personal bad play. Megaera couldn't be bothered to swap out Combust glyph and Ji-Kun kept letting myself fall off platform during downfall.
Honestly if you are able to play decently I'd say you'd be able to go Fire with ~500 iLvl, provided you can hit ~31-32% crit fully buffed, that's what I did.