Saruman is an incredibly under-rated ally. I hardly ever see him in play, despite the fact he's kind of amazing. I attribute this primarily to people's knee-jerk averse reaction to the Doomed keyword, with perhaps the secondary consideration that in contrast to his obvious counterpart Core Gandalf his enters play effect targets encounter cards rather than improving your own board-state via threat reduction or card draw, and as such is less universally applicable. On the other hand though, he's also cheaper in resources - any three hero deck can play Saruman any time they like, and I don't feel like the Doomed 3 is out of proportion with the benefits of the ability, which while it's not useful all the time, is certainly useful quite a bit of the time. Admittedly because of the Doomed he also pairs less well with Sneak Attack than Gandalf, which may be a factor.
Stats-wise he's down 1 and up 1 compared to Gandalf, meaning perhaps more of a focus on combat, but 3 is still respectable. Obviously he'll pair incredibly well with any means of getting extra actions out of your allies, such as Galadriel and Narya, letting you use two or even all three of his rather impressive stats in the one round for which he's in play. What really pulls attention and should make you consider the White Wizard though is of course that interesting ability to mess with the staging area.
And what an ability. While Saruman is in play, a card in the staging area is considered to be out of play. Obviously there are restrictions here - it only works on non-unique enemies and locations, and for there to be a valid target means you haven't engaged the enemy or explored/travelled to the location on a previous round. Unless using shenanigans like Vilya or stomaching the Doomed on a Sneak Attack you can't use this to put a card out of play the same round it was revealed, you have to wait. But on the other hand, there are enough annoying enemies and locations that you can leave in the staging area that you should have potential targets - and if you don't have any targets as the staging area is clear, that probably means you're doing well so a dead card in hand doesn't matter too much. But more to the point, consider what that ability equates to - the number of other cards you'd need to replicate it:
- Since the location/enemy is out of play it doesn't contribute its , so effectively a Secret Paths/Radagast's Cunning
- If the card has an unpleasant Forced or passive effect on it, you ignore that, so either a one-round Thrór's Key or Revealed in Wrath.
- If it's an enemy, you also don't have to make engagement checks against it - Noiseless Movement.
So that's 2-3 cards costing 2-3 resources to replicate the ability Saruman gives you all in one card for 3 resources and 3 Doomed, with a very powerful statline attached. OK, it's worth noting that since the location/enemy is out of play you also can't do anything to get rid of it in the long term like place progress or deal damage, but you can work on that subsequently after having a round of complete respite from it. There's also an extreme case - if your quest advancement or even victory depends on there being no locations/enemies in play, then Saruman can let you loophole that condition as if the last card of the relevant type is the one considered to be out of play for his effect it won't count and thus you advance/win without dealing with it. Even outside of that fairly rare case though, the ability to completely ignore a card for a round is incredibly powerful, and so I would say Saruman is well worth it.