Following situation:

I got Howlrunner with Elusiveness. She is under attack by a X-Wing. The rebel player rolles

hit, blank, blank. The rebel player uses his TL token on Howlrunner to re-roll the two blank results. The result is hit, hit, hit.

May I now use Elusiveness to force the rebel to re-roll the one dice that wasn't re-rolled using TL?

Pg 11 of the rulebook: Modify Attack Dice. The defender must modify the attack dice before the attacker modifies the dice. So in your specific example, it is too late for you to modify the dice by the time the attacker has rerolled the dice. You needed to use the card's effect before the attacker used TL to reroll.

I concur with the previous poster... and the rule stated. You would have needed to use Elusiveness to reroll the one hit (preferably) before the attacker rerolled using the TL.

Yeah ... but in most times players don't hesitate a second before re-rolling or modifying. This leaves 0 time to think about wether should re-roll or not. Next time this happens I'll make my opponent eat his dice....

Besides, I wouldn't have used elusiveness for a single normal hit.

In fact, in the extremely rare occasions I equip it, I use for critical hits almost exclusively.

Yeah ... but in most times players don't hesitate a second before re-rolling or modifying. This leaves 0 time to think about wether should re-roll or not. Next time this happens I'll make my opponent eat his dice....

I think many of us get used to the defender not having some effect that can modify the attacker's dice and therefore tend to forget.

Those are definitely steps that get overlooked out of careless habit, simply because there are relatively few abilities in the game that directly affect the other guy's rolls, as opposed to your own. But the other guy always has a chance to modify the results of your roll before you do, and vice versa.

Attacker rolls? Defender gets first modification.

Defender rolls? Attacker gets first modification.

There are only a handful of things in the game right now that use this, so your best bet if you bring something like Elusiveness, is to just point it out ahead of time and remind your opponent up front that you get first dibs on modifying his attack rolls. And of course remember that if you reroll one of his attack dice, he can't reroll that same die again.

I did something similar for a while with my AdvS B-Wing squad. When AdvS was newer, and I was more prone to landing on rocks, I had confusion come up a couple of times where opponents - one at Worlds - insisted I could not barrel roll off of an asteroid before executing my maneuver. That is totally legal (so long as you can do so without the template overlapping the obstacle you're on - if you land square in the middle, you're SOL) so for a while I just got in the habit of saying up front "ok, just so we're on the same page with the Advanced Sensors..."

Yeah the other guy is supposed to give you a chance to make changes to his dice before he does anything, but because there's so few effects that allow this, and those aren't used often, we tend to skip over it.

It's like rolling defense dice before the attack dice have gone though the process. You're not supposed to roll until both players have had a chance to modify the attack roll. But I know sometime I and others I play with tend to roll sooner then they should.

I always wait with my defence dice and generally get opponents to wait with theirs. It can make quite a difference on whether they spend focus/evade or I spend focus/target lock...

Yeah I occasionally play with people who rush the rolls, and so I'll generally just tell them I'm thinking quick while I debate if I want to modify.