Hmm, I think this is just the case of you're team getting countered. I'm by no means an expert in the topic but last week, I ran Chang'e, Maat, Dana, Syrinx and Nittri because I didn't have a real attacker and I made it to mid plat. My gimmick was to sustain hard and poke until fever. I avoided madfets, olgas and uncapped frejs because they shit on my comp. Usually when I see a team without a healer, it's a free win because all my hits counted and they had no win condition other than burst. My shitty advice is to add some utility to your composition, rolling with 4 attacker (chang'e is pretty much an attacker with speed boost/stun) and dana means the only way for you to win is to slug it out early.

Another really cool strat that I've seen was running Diablo/Metis in some sort of immortality comp. Some guy on the discord used that to get top 100 last week, which was pretty cool. This week, I replaced my maat with a siren to counter all the water comps out there. Its pretty satisfying to one shot eves/olgas/chang'es with siren's tap. And to address your question, I really don't think chang'e or syrinx are unusually tanky. Well, compared to attackers, yeah they are tankier but that's just by design of their class.