is 5% open wounds enough for ubers?

first time running ubers, so any advice is helpful.
im a smiter

From

Blood Belt?
And no Drac (25 OW)?

I would say too risky without

Life Tap from Drac.

Well, the lifetap you could get from Exile. Or a

Wand. Or ...

OW itself isn't there to do any real damage. It is solely there to stop the ubers' regen (because PMH doesn't work on them).

Plus you can't "double-OW" anyways so any OW that gives "enough uptime" is enough.

To add some math to that:
OW lasts for 8 seconds.
Using

Smite, you hit 100% of the time so "no application due to missing" can be ignored.
As a result, when you look at the actual odds of re-applying open wounds before it runs out, you get the following (assuming 6 frame

Smite):
Based on that (as well as personal experience) there will be gaps at 5% during which ubers will manage to get a bit of regen in but it is still sufficient to get them killed decently well.

Personally, I keep my smiters at 10% OW (thanks to

Gore Rider) which is more than enough even if you run a setup that has you dropping

Fanaticism (and hence down to 7 frame smites) against meph.

What armor are you using? A Duress is cheap to make and will cover your OW needs nicely, 33%, while adding another 25% to crushing blow.

With

Smite you hit 100% of the time but your attack speed affects how often you hit, and that's an important consideration.