Yea no star destroyers shields are for blocking debris and small to medium asteroids and lasers (any asteroid due to cosmic speeds+ mass is roughly 500x more powerful than a NUKE of the same yield) yea hyperspace and slipspace are different but BOTH are FTL and star destroyers are faster. As for ground war ild love to see afew ODST teams get PWN3D by a legion of troopers and 4x AT AT (the battleforce aboard 1x star destroyer) and star destroyers ARE DESIGNED to sterilize the surface of a planet till its devoid of all life (just 1x btw)

So are covenant troop ships. We are thinking of humanity and covies as one army. The shields is an interesting point, but both human and alien forces have used EMPs alongside some of their salvos. Also, ODSTs are deployed in the hundreds for assaults and are trained to be guerrilla fighters. A single soldier with a grenade, cutter and grappling hook had no problem taking down an AT-AT and neither should an ODST with satchel charges energy blades and magnetic gear. Your also forgetting the SPARTANs and normal Marines to add as force multipliers.

Your also forgetting they have to get thru nearly 2000 trained troops/galactic marines with blasters, heavy blasters, blaster turrets, snipers, shock troops with rockets, and each storm troop has a grenade charge that's double the yield of a thermal detonator, an they gotta chew through that before they get to the at at.

Or drop an HEV pod right on top of it. You're forgetting how ODSTs get to planets. They're bloody missiles. And it would be the marines that would have to get through it. And the clones aren't a threat, they can't hit shit.

If its FASTER THAN LIGHT its ftl: http://www.fatwallet.com/blog/fastest-ship-in-the-universe/