Problem with the D'deridex is pretty much the problem with a lot of fed cruisers.
Cruisers generally rely on shield and hull tanking. To make them viable at DPS, one must be lost. Now for PvE this isn't a problem but for PvP this will geneally mean you're cannon fodder for escorts.
Actually cruisers relying on tanking is a problem in PVE as most endgame content is big on DPS to get it done before time runs out.