Well, that's not how we say it. Generally, its all before the dice get rolled, and it goes something like "*insert attack here*, 10 on a 17, need a 7 for 3". We're pretty consistent with announcing damage (potentially) dealt, or announcing damage taken after factoring in reducers, etc., like" ...need a 7 for 2 after Toughness" or " for a possible 1 after Imperv".

If you were playing with my group, you'd see we're pretty good about keeping it clear. And we're even better about it when playing other/newer people. But yeah, if its not done consistently, it could be a little confusing. Even then, a simple "is that 3 before or after Invuln?" is worth making sure everyone's on the same page at every step of the process (to me, at least).

I don't think I've ever played a game of Heroclix in my life where both players didn't do the math before rolling the dice. You both anxiously wait to see if the number needed comes up. I feel like that's part of the fun.

One of my players was a man of action. He'd just point at one of my characters (possibly saying "Boom!" but not more than that) and then roll the dice. I usually interrupted with a "Wait... what exactly are you doing?"
I like it when both players can agree on what roll is needed to hit. You never know when there's some factor you haven't taken into account.

like a reminder that I'm standing in hindering so I'm +1 defense.

and a reminder-reminder that you ignore hindering for ranged attacks.