Originally Posted by pf

If a trinket is modeled correctly in the spreadsheet, adding haste ratings will work just fine with a trinket like the dragonspine trophy. However, instead of it being modeled correctly, it might be just estimated in which case someone should fix it up correctly.

Anyway, on the topic of the thread. Haste rating does diminish in relative value with each point added, whereas regular % haste modifiers do not have the same relative diminishing return. Simply put, haste rating is additive whereas a haste modifier is multiplicative. Another way of putting it would be 10 haste rating grants you 1% haste at base attack speed, but after say 30% haste worth of haste rating, you still go up by 1% haste, but only gain .77% attack speed instead of 1%.