The old Abyssal Scepter was a decent defensive item for mages against mages. It did favor close ranged mages with its passive, but the relatively defensive nature of the item with its 60 mr was a good amount to protect mages from each other. They could still be killed after some harass, but it helped to avoid 100-0s.
The new Banshee's Veil seems a little too strong in this department. In a mage vs mage matchup mid-lane, if one of them rushes this (maybe after lost chapter), the other will have nearly no chance of killing them. First it will take one spell hit to remove the shield. Then you have to deal with that same 60 mr as before. Then if you let up long enough, miss too many spells in a row, or they just back up a bit, the shield will come back again to deal with.
Honestly I'm all for something of this sort for mages, but it seems like it'll be a bit overbearing for mages to fight against. I'd knock down the mr a bit (maybe down to 40 or 50?).
Now all of that is my relatively unbiased view on the item. With my bias, I'd want some further changes, like removing the CDR on it as well, and increasing the AP a bit (up to 70 or 80).
Overall that would be:
70 or 80 AP
40 to 50 magic resist
Unique Passive: Spellshield