839 MA ohkos both types with EA but not Scorching for the stronger ones, I suggest at the least 800+ MA (820 or higher likely) for a Fire/Elec Sheep/Wizard, and if you use Scorching, to Scorch and put some distance from it, as to not die from the Kerbs, usually if I run to the other side they tend to forget about me. I found no trouble surviving with the amount of MA I had, and roughly 2.7k DP.
I wouldn't really suggest any less MA though, really. This is all just my opinion based on my MA and stats to throw suggestions to people asking about Elec/Fire, and assuming I can recharge soon I can probably (hopefully) get to the range where Scorching ohkos, I'm guessing it's close to 900 MA.
None of this is exact, but hopefully a tad more visible in this thread. Not something to be accounted for in the OP, but something to help guide people to about where they want to aim at for MA, which is more than 839 MA if you plan on using Scorching.
This is how much health the higher resist Kerbs have after a scorching. My effects are off, but I'm the only one grinding there and I know my EAs ohko
I'd peg the MA needed to ohko with Scorching at 850+