If my Tomcat moves into flame thrower range of a linkteam, but the closest guy is blocking LOF to the rest of the team, are they all able to dodge or is the only action the back 4 can take to declare change facing as I have triggered an ARO without them having line of sight to me?
If its a link team of 4+ they can and you're within ZOC they could hold then dodge. Otherwise as you described.
Note that the only difference between all dodging and all changing face being the one model with LoF having a malus on their roll in the latter case.
There is the matter of Fireteam Integrity and the Majority ARO rule. Getting most of the fireteam to declare Change Facing and the model in front to declare Dodge can be pretty useful to reducing the fireteam membership (even if those members would be rejoining automatically if they survive the turn). That trooper in front may actually get stuck choosing between "No ARO to stay in the fireteam" and "Dodge and leave the fireteam" if everyone else is declaring Change Facing. You really don't want to have fireteam members getting in each other's way in this sort of situation.
If you're confident you're within ZoC you can delay and then dodge when hit by the template, as described above
He could also just declare Change Facing preemptively. He meets the second clause for declaring that ARO.
Yeah, you really want to go with the Dodge over Change Facing in this circumstance. SSL1/2 means that you Dodge templates from out of LOF on flats rather than -3 whereas Change Facing's -3 is hard coded in so SSL1/2 doesn't affect it. So for the troopers with no LOF: A. inside 8" declare 'delay ARO with SSL1' and then after getting hit by the template declare Dodge on flats. B. outside 8" go 'no ARO' followed by Dodge on flats. For the troopers with LOF. A. Inside 8" 'delay with SSL1' and then after getting hit by the template decide whether you want to preserve Fireteam integrity and Dodge or threaten the attacking Trooper by declaring something else (and know that you'll split the Fireteam) B. Outside 8" risk splitting the Fireteam by declaring BS Attack (or something else) or preserve Fireteam integrity and Dodge
Just remember that if you split off more than one from the full link you'll lose 6th sense and take the -3 penalty anyway.
