Am I being too tough on my players?

[Errant]

... The hobgoblins will take at least a week to march there once they decide something is wrong and this kingdom is big enough to send LOTS of hobgoblins. In addition, there are two other parties trying to get to the tomb but each is at least a week behind the party...

Are the two other parties necessarily hostile to the PCs?

Could be, one or even both (if the hobgoblins mass strongly enough) could be good/neutral &/or potential allies.