From my perspective, the BS has absolutely nothing in the AA that is "mandatory" from a normal gameplay experience. They have all the tools they need in their skill trees. The AA abilities they gain give them some additional healing options, but they are almost worthless without heal rating, and fairly useless in PvP. The higher tiers of attacks are nice to have, but only nice to have - not essential.
The only exception is the same exception for just about every class -- the CC break ability in the "archetype" category for every single class can be invaluable in both PVE and PVP. I recommend getting premium for at least one month after hitting 80 in order to farm enough AA for that specific ability (along with some of the other nice to haves). Be it on a rogue, priest, soldier or mage, having an additional global CC break / immunity can make all the difference.