Even in HE, the outs formula misses on backdoor
hands. This compounds in Omaha, and then compounds a bit more in O8.
In O8 it gets much more complicated as it is often some backdoor variant we didn't see, and thus add in to our calculations, that wins the hand. Also, it could easily be the case that with certain hands you have so many outs that you will arrive at a formula solution which exceeds 100%.
AA23 double suited might be one with a flop of 2 of your suit and those being 45xx.
So any suit(9 outs),
A23 (8 more outs)
44 or 55 on the turn/river, along with 6's,7's,8's (12 more outs) and all of a sudden you have 29 outs X4 = 116%.
Granted I double count a few of those outs, but because O8 is a split pot game, with 2 ways to win, I feel semi-justified doing so. Caps point about the quality of those outs improving you hand to become the winning hand are very important. Many times you can improve you hand, but not enough to win the pot, or your share of the pot. Then add in the quartering and the formula falters a bit more.
The point is that that formula doesn't work quite as well for O8 games as it does for HE. But for quick guesstimations, the formula is better than anything else I've seen.