The largest, toughest, most powerful ships in the game will still be fast reaction "blob" forces and that's just wrong! The only difference is they'll only be able to react faster than just about anything else within a shorter range, but within that range they'll still reign supreme.
Just like in real life, the drawbacks to really big ships (besides expense and manning requirements) should be that they're slow, ungainly, difficult to maneuver and highly dependent on consorts and logistics (support and supply lines that is, not magic healing ships).
They're great for defense because they don't have to move very much or very far and it's much easier to support them close to home.
They can be good on offense too, provided they have time to get where the fight is with the necessary consorts along and with proper (hopefully secure) support and supply lines in place. They work well against more or less stationary targets that can't move (or at least can't move quickly) and against other large fleets also containing very large ships.
What they are not is a quick, fast reaction force. They *aren't at all good at catching small, fast forces which can simply evade and stay out of range, though a component of the support fleet consorts may be.
Stop messing around with half measures CCP and do the right thing. Remove jump capability from everything larger than a Black Ops battleship and put capital ships into the role they belong in.
Edit: Found a comment over at Mabricks Mumblings by Druur Monakh who says it better than I did.
In RL, battleships have fallen out of active duty because they are big, lumbering hunks which take ages to get to their destinations, and then easily fall prey to superior numbers of smaller, lighter vessels. Aircraft carriers are big and lumbering as well, but at least they can bring numbers of smaller, lighter vessels with them. But even aircraft carriers are not sent from one end of the globe to the other willy-nilly – the travel takes time, they can be intercepted en-route, and if the carrier is sent over-there, something else has to step in to do the carrier’s former job here.Druur gets it!