Question about using tier 8 quality gear and haste for Herald of the Titans

[Snorri]

Tomorrow me and a raid group are gonna try for Herald of the Titans achievement. I'm retri specced. I have collected a good amount of tier 8 and other items of ilevel 226 for the job. I ran RAWR to see what I could improve. It showed that I would do quite a lot more dps if I used a haste elixir instead of a flask of endless rage. Is this correct? I do have mixology bonus.

I haven't raided with tier 8 gear for a long time, but I don't remember haste being that good, right? Haste has only been okish for retris for a long time. It wasn't until tier 10 it became a lot better due to the tier 10 bonuses.

Thanks in advance