You know i use my froaen orb sorc on meph all the time and she handles it quite well, i've tried running it with and without plus cold gcs and i find that the extra punch from the gc's is really needed to beef up that orb damage. Iget some faster cast rate from my magefists,full tal set and a nice act2merc for a meat shield.
I've never tried a blizzard sorc, probably better, and i dont like meteor too much.
So Frozen orb all the synergies maxed, and a couple of cold gc's will do great.
But as i said i have never done a blizzard sorc and correct me if i'm wrong, i think it just may kill that big bug a little quicker.
Blizzard works really well because it covers a good radius, and a high level CM will drop Meph's resistance down to nothing or less, making it really easy to kill him. I tried both pure fire Meteor/FB sorcs and Blizzard/Ice Blast sorcs, and Blizzard takes him down much faster in my opinion. In NM and Hell, Meph's Fire resists in NM and Hell make it much harder for fire to damage him.
Once again, it just depends on your playing style.
As for stat points.
Strength - Enough to wear Skullder's or Monarch Shield if you're using Storm Shield or a Spirit monarch.
Dex - Base, enough for Wiz Spike, or enough for full block.
Vita - Everything else
Energy - Nothing
My orber kills meph no problem in around LESS then 10 seconds flat. With over 650%MF sacrificing no time at all. No gcs, Orb damage is around 700 per shard.
If your going to run anything else then meph i probably wouldnt advise using an orb sorc though, its tried, trusted and true at only doing one thing, teleing to meph, killing him quick, and repeating.
Although I am still able to countess/nith/summoner/diablo/baal and even hell rush, just at a slower speed then maybe a lightning sorc or anyother sorc for that matter, because I depend on my merc to kill every single cold immune.
My sorc runs only with 50% cast rate, and has never died teleing there since she was in the late level 70's, now she is 92, and she only levels by mfing, no baal runs.
I find having lots of Mf helps more then sacrificing it for damage and speed, because your not killing any monsters, only Meph, which gets taken down too fast as it is, I get kicked off of Bnet all the time for joining games too fast.
On a side note, she also excels at doing hell andy, summoner and all of chaos sanctuary except oblivion knights.