1) These are only preliminary patch notes; going off of what's been datamined it's entirely possible that Firelands will not be the only raid and that ZG/ZA will not be the only 5-mans (there's supposed to be another Abyssal Maw instance, remember?)

2) Firelands is only 'rehashed' in that a character is being reused as a boss due to the last go at him being nothing more than a setback. Everything else about the raid is completely new, as far as we know, and there's no reason to assume otherwise.

3) ZG and ZA making a comeback should not be a cause for concern, as SFK and DM being retooled for Heroic play set a precedent for early story dungeons being completely retooled for this expansion. Nobody seemed to have a problem with it then, so I don't see what the problem is now. You also do not know if the new instances are in fact just retooled a la SFK and DM or if they've been significantly overhauled in other ways due to their size compared with other 5-mans. Basically, you're bitching up a storm with little to no details whatsoever.

4) The other possible raid for this patch, the CoT War of the Ancients instance, will be completely 100% new. As the area in which the event occurred is currently underneath the Maelstrom there is little chance for existing terrain being reused for it, and nobody knows if Archimonde will actually be the final boss or not (although I'd assume he would be).

tl;dr: you're whining about things you don't have complete information on. Shut up.