I concur. Max Chao in the meantime. The rough odds are you’ll get four 3* ascension materials (Magic Orbs) for each 4* ascension material (darts), so you have a pretty good chance to get Chao to 4/70 and Poseidon to 3/70 before that 6th dart rolls in.
I personally see about a 3-1 ratio due to fighting 6* Titans and not skipping chests very often (I’m a gem-pincher, a’ight?!), but still the math makes sense.
Chao is a decent yellow hero and arguably the best one for offensive raiding, especially with emblems. He’s not the best 4* sniper in the game by any stretch of the imagination, but he’s the only option you have for yellow, unless you’re lucky enough to land a Guardian Jackal, so work with what you have.
And yes, when you get that 6th dart, I’d go with Poseidon.