Cyclo-cross versus Cross bike
I don't know why, but Merida seems to be confusing the terminology. Cross is typically short-hand for cyclocross and used interchangeably. If you told me you were looking for a cross bike I would instantly assume you mean 'cyclocross.'

Cyclocross bikes, are somewhat race specific and sacrifice suspension for speed. Most cyclocross forks are going to absorb some of the vibration, but not much.

If your back is giving you trouble, I would go with something that does have front suspension like the XT you had.