Mage's Attendant: Good, but limited fodder. Might make it into a Party-themed deck, as it gives a rogue and a wizard.
Rob the Archives - Another solid red "draw" card, as it's not part of red's color pie to exile cards & get to play them, opposed to actually drawing them. Is also a good work around of cards that limit you to one draw a turn. I can see this as being part of the fast and mid-range red or red/x color(s) decks in Commander.
Mage's Atenndant is a pretty sweet, versatile card. Decent MV to P/T ratio, multiple bodies with multiple relevant creature types, and a white counterspell that fits better in white than blue. I like it a lot. Not sure how great it is, but it's definitely interesting.
Its just flat out "good" , at least in standard it will carry some decks, as this can simply "delay" a wrath effect and puts a 3/2 and a 1/1 on the board for 3 mana and it works with all kinds of mechanics in the set (sacrifice for Casualty, creatures for Alliance, etc. etc.).
Balanced it would be a blue/white multicolor card and probably cost 2WU , that would still be good, but as it is, its just pushed by quite a margin.
Rob the Archives can be a draw 4 in some combo decks, so thats nasty as well.
At sorcery its a bit less amazing, would be a lot stronger as an instant to turn a jump-blocker/attacker into more cards.