Finally got GAS: the most painful event so far in SWGOH, it really is all about RNG & the mods. In the end, I had an R4 Asajj, R4 B1, R4 Droideka, G12 B2 & G12 Magnaguard. A fellow guildmate provided the most succinct mod suggestions:
Biggest things to remember, as much protection primaries on Magna with a health set, speed/potency on B2, offense/speed on B1 and Droideka. Remember to retreat if things don't go well in opening salvo. Stun Rex with Magna, kill Fives and go to town. Use Asajj to take away buffs and then AOE for defense down. Don't AOE if they have retribution.
(You don't need Magnaguard's zeta; Droideka's zeta isn't required but it will definitely make the event easier (and I like the zeta for use in a GG squad anyway).)
P4 is all about the opening salvo, just like the Chewie event. If they Daze, Stun, or go after B2 or B1 and Magna doesn't taunt or counter, RESTART
: you'll never win since Magnaguards counter is crtical. If they go after Magna and he counters, then you have your shot: he'll absorb most of the hits to let you focus down on GAS, then 5s, then Rex, Echo and Arc. Get stuns on Echo if possible. If at any point that isn't happening, retreat and start again. (Remember, this is all about RNG and mods assuming you have a good squad.)
Stunning Rex is a MUST; in my experience, you will know RNG is with you when you take down GAS w/out using Droidekas middle ability (Reconstructive Revolution), saving it to one-shot Fives.
Its Just Ian - GAS Phase 4:
Asajj: mod for fairly high speed, good protection, crit chance, offense (2:15 in the vid)
B1: Offense, offense, offense. Speed not a big deal. (8:30 in the vid)
B2: potency, protection, CA. Speed not a big deal. (7:35 in the vid)
Droideka: offense, tenacity, mod for a bit faster than Asajj and Magnaguard. (5:15 in the vid). Protection not a big deal.
Magnaguard: high protection, speed (210 or so), crit avoidance (CA arrow if possible)
Good luck w/this painful event...GAS is very important to go against the GL's.