Not sure what you mean by fried? If you vaped 30ml already, that means you obviously prepped the coils cotton properly. So do you mean dry hits, or just decreased vapor production? Is your juice really dark, gunking up the coils? I really only use the Eleaf .5 ohm titanium coils in my Mello as I mostly run in TC mode. I run 30/70 & 20/80 pg/vg and the juice feeds well, though I'm not a chain vaper. For the most part these coils are ok, but the one I'm using now was a problem early on, high ohms, cracklings, it was odd. Didn't want to throw it away, so I took it out, pulled the 510 pin out, put it back, reprepped the coil with juice again, and it seems to be working better, ohms now proper as well. Point being, the prebuilt coils can vary from one to another, some just suck. But a good one should give you a lot more vape time then 30ml. of juice!
The Mello is not one of my favorite tanks so I put them away for awhile. Just recently giving them another chance as I'm tired of my Cubis tanks flooding. None of these tiny tanks have the flavor of my Merlin, or Kayfun 5, but for certain pocket carry mods, like my new Target Mini, a small tank is called for at the expense of flavor.
As far as the available RBA's, I collected all 3 types, to use when and if the FDA ban makes getting prebuilts hard to buy. So I can't say I've used them yet. The Eleaf one seems the worse build wise. They are cheap, so if you find you like the Mello, try all three. Wish I could be more helpful.