Rookie Uber Questions

I tried taking on

Uber Tristram last night for the first time. I didn't expect to beat it, I've just never done it before, and wanted to at least experience it. This isn't a "how do i beat ubers" question - I know there are builds that are meant to be able to farm Ubers (and my

Strafe Amazon isn't one of them), so if I really wanted to, I could build a Smiter and follow any of a million guides - I'm more just curious about some of the mechanics involved.

I don't think I had a shot at ever killing

Uber Mephisto - the million skeletons are basically chaff to

Strafe, and you can't steal Life/Mana from them so I had no sustain.

Uber Baal, though, I was able to hold my own and stay alive, but I couldn't overcome his regen. I was poisoning him, and that was working at first, but it seemed like the poison duration kept getting shorter and shorter - by the time I got him down to 50%, he'd basically flash green for a frame and that was it, so he was just able to regen back to full health.

I think the correct answer is actually Open Wounds, which I only had at 10%, but what's up with that poison length getting shorter? I can't find anyone mentioning that in any guides or wikis or anything. Is that a thing? Does he somehow increase his "Reduce Poison Length" stat during the fight?

Also,

Guided Arrow, which is supposed to always hit, kept appearing to miss. Is that because he's Blocking them? If so, how do *real* Ubers builds deal with that? Is there a way to overcome or reduce a monster's Block chance? I'd think you'd have trouble reliably proccing Open Wounds if the Block chance was as high as it seemed?

I also wasn't really able to keep my Merc alive - can a sufficiently geared Merc actually stay alive in there, or are they just always gonna die, and your build just doesn't assume you're gonna have an alive Merc?

Without Open Wounds or +Poison Damage, how do casters stop the health regen on these guys? I'm pretty sure I read that Prevent Monster Heal doesn't work on them, so does a caster just have to be able to outpace the regen, dealing enough DPS to offset it?

Anyway, my cats managed to pull the computer plug out of the wall, thereby freeing me from the endless loop of getting

Baal down to 50% only to have him regen it all back. I take solace in knowing that even if I was gonna be able to beat them, that power plug pull would have stopped me anyway.

Thanks for reading, hopefully someone can shed some light on what I saw on the other side of that red portal.

Lot to unpack there I guess.

First off, the solution to your lack of leech is drac's. Or

Life Tap in general. That's based purely on the phys dmg you do, rather than being affected by their drain effectiveness. Mana, if need be, you could aid with damage taken goes to mana.

With regards to their regen, you are correct. PMH does not work on ubers, just on dclone. Thanks to that, you need either poison or open wounds. Meph and

Lilith are poison immune though so to cover it for all of them, you need open wounds. Better for dmg anyways since the other 4 - while not immune - still have 75 poison res.
OW lasts for 8 seconds so you do have quite a bit of time to re-apply and hence don't need anywhere near 100% chance to proc OW. But you do need to actually hit to proc it so when considering how much you need, also consider a) your hit chance against them and b) target block chance.

If I remember correctly, diablo is the only one who actually has block, at the usual 50% of it.
The only real way for you to counter block is to use attacks for which it doesn't matter. That's some aoe moves,

Impale or for "real uber killers" the obvious

Smite and so on.

If you can get your resistances to a decent enough level against uber meph's

Conviction and get a source of

Life Tap plus get your mana problems solved (which should all be relatively easy), ubers are actually pretty easy for non-CS zons as well. You can just stand there and keep strafing. Or you get a point in

Impale (yup, 1 is all it takes) with titan's+shield on switch.

Keeping your merc alive is a fair bit harder as a zon. You can either go for a true uber-merc build (which is silly and usually A5) or you at least pre-buff him with Treachery though even that has a good chance of running out again as a zon. The main issues for him are a) meph's

Conviction annihilates his res and b) if he ends up focusing on one of

Baal's phys immune adds, all his leech goes away, even with

Life Tap.