I'm not really surprised about Undertaker, due to the fact that while he's wrestled a match here and there after Wrestlemania 26, he's still resting and taking his annual time off, and I think that's just fair, so no need to have him on the card, even if he's being advertised, the only way it could work is having him pop up after one of the matches, and that's probably the only way it'd make sense to have him pop up.
Sheamus on the other hand, I kinda agree, I'm a little surprised he's not on the card, but then again, who was he to wrestle? the top guys who could properly put him over is already busy with their share of feuds, and it would make absolutely no sense establishing Sheamus as a main eventer if he was to battle some mid-carder, and as i stated, it's fair that Undertaker isn't on the card, so it couldn't even be Undertaker vs Sheamus.
But in the end, I'm actually somewhat fine with Sheamus not being on the card, while it's not exactly gonna establish him more, I just think that the feuds that have been put on the card already makes up for it more than perfectly.