I think we're talking Schrödinger's box office draw here. In general terms neither RDJ or Evans have box office pull, but in MCU films they absolutely do.
There's a broader question about whether anyone is guaranteed box office gold anymore, even Tom Cruise isn't guaranteed to put bums on seats, but I do think RDJ and Evans will (purely in an MCU context), whether the number of tickets that are sold the back of them returning compensates for the insane amount of money they're no doubt both being paid is another matter.
Of course maybe Avengers: Doomsday's box office doesn't really matter*, it's about reinvigorating the MCU going forward so it might be seen as something of a loss leader.
(*Obviously it matters in that they want it to be wildly successful, I just think they're smart enough to realise that given it's likely budget it could never count as a box office smash)
Also,
@JD you're not crazy, or if you are I am too.