Grapple moves...context sensitive?

The animation that plays when someone attempts a grapple with no target in range (the grabbing at thin air motion) can be seen by opposing players, correct? So we'll be able to tell if someone is trying to grapple us instead of shotgun-ing it out as Supports, right?

Can you grapple while taking damage? For instance, if I'm an Assassin and I'm slashing and going crazy at this dude, do I need to make sure I stay directly behind him so he can't turn slightly and grapple me?

Yes, there's a grapple-miss animation that plays when you try to grapple and miss. A miss will also cost you a slight amount of your skill so you can't spam the grapple button, you have to time it.

You can grapple most of the time an enemy is in range and your skill is ready to be used, doesn't matter if you're taking damage. There are a few exceptions... like the target is already in the middle of a grapple, certain skills are happening (like being the the middle of a Gunner slam or the Tank's Jet Gun Spin) or the target is deployed.

Do any grapples require you to shoot (maybe a shotgun to the face or something) and if so, if you are out of bullets will you do a different grapple?

You can't shoot during grapples, so it's a non-issue.

Ok, because in the Character Montage Video the Support does this grapple on a tank and i thought when he shot him in the face it was part of the grapple. (just watched it again) and it wasn't. But thx