Filir should have more flee than vani at equal level with Accel 1 up, and hence should do better w/regards to dodging attacks. The vani will of course take less damage, since vani has high vit, while filir has almost none.
But the thing is - for unattended leveling in OD2, your filir shouldn't be dying (if it is, there's likely an AI or AI config problem), nor should a vani. And in attended leveling, homun deaths don't matter (just res it - you can even start casting res as you see it's about to die, so it'll be dead by the time cast bar finishes and ressed even faster), and DPS and SP pool is what matters.
evolved filirs ASPD goes up from his unevolved ridiculously slow(for a supposed AGI class) aspd of 173 to 183, which is alot better (im not sure what vanils evolved aspd is though). Unfortunately his flee doesnt get much better and like you said, he has almost no vit. The problem is Renewals game mechanics making flee garbage. Filir deserves a dodge update to work as intended if they arnt going to give him any vit.
I 100% agree with you though that he is the fastest leveler, but only if you are willing to spam homunc resurrection over and over.
I think the odds of ever seeing our homuncs fixed to work right are pretty slim though (that poor unicorns interuptable aoe spell lol). I just made this thread as a warning to all the poor alchemists starting out and thinking of getting filir. They need to know what they are getting themselves into