I think the Iceni is more comparable to the Chimera than the Diomedes, to which end it's still clearly obsolete. And since it doesn't have the multirole ability of the Deimos or the carrier capacity of the Orion, it really has no place in Sol.
Though if there's one thing the GTVA should have learned from it is that if you have something that you don't want getting disabled, like, say, a logistics ship, it should really have redundant engine subsystems.
it's only weakness is that it lacks flak of any kind. It'd probably be chewed up by Federation fighter superiority.
The Iceni has both flak and AAA during the SOC loop, the only time it's actually used in combat.