Glad I'm not the only one pulling my hair out on this one. I have been setting up on the right with d1 haarken, d2 aethena, d1 sho, g1 Tyrant Guard and d3 Eldy. Getting to within about 10 templars of completing, it's the only mission left before 100% for me. I've been killing templars on the bridge, I'll try only killing high damage ones as one of your other comments has suggested.
Best of luck. I think the key for you will be to spread the damage taken among your heroes so that you have as much time with everyone alive as possible.
Swap Calandis out for JZ, equip her with your best blocker and take her passive as far as you can. You can then use her as a punchbag with TG behind her. The other three you want to alternate between taking cover next to TG and killing the dangerous enemies. Jaeger is a massive pain and you'll be in big trouble unless he uses his active on your toughest character
Nah, Snowprint doesn't hate us. They loves us. Or at least they loves our wallets and wants to motivates us to gives them more monies to buys and upgrades ALLLLL the heroes to completes the eventses. 😅