1. I havent actually bothered to hire any mercs with Sandeep in my 30 odd games with him and never once felt I was losing out.
2. Favourite Beaters would be Banasuva, Howard, Joss and Arcane Emissary with Cassandra kind of pulling in here a little. I tend to find I can go light on beaters with Sandeep utilising models such as December Acolytes and Silent Ones combined with Sandeep with the Commands upgrade. Having a Summoned Metal Gamin with Commands in Wind moving around those models plus a minion copying Arcane Storm covers a lot of the damage dealing required.
3. Favourite Henchmen woudl hands down be Cassandra, seconded by Myranda and I need more games with Carlos when he comes out as he looks very tasty too.
I have run both Angelica and Cassandra in Leave Your Mark games, its not and either/or option Angelica helps out slower models such as a Silent One and Arcane Effigy or even Pushing about the Emissary to line up a charge while Cassandra is always very independent.
Heals are always coming from Silent Ones
I dont need mercs at all with Sandeep, if you want a Sniper take the aggressive one we have with a December Acolyte