Doesn't work that way for haste because the way it's calculated is different. You have to use the formula I gave you earlier.
Added haste/(100-total haste).
85.19 to 88.68 is adding 3.49 haste.
3.49/(100- total haste, including what you added)
3.49/(100-88.68)
3.49/11.32 = 30.83% increase (Fyi this is why the hard cap on haste is 80% because when it was higher, things just got plain insane.)
If you're fine with dealing lower damage, go right for it. I'm not here to tell anyone how they should or should not play, but if they want to perform better, I will post how you can achieve that. From there, you can decide whether or not you want to.