For only and exactly the same reasons cruisers would have to escape from a battleship group now. If you’re not looking at escape or pursuit, warp speed’s not a consideration anyway.
No, they don’t. Nothing represents ‘most battleships’. Does a Typhoon represent a Hyperion terribly well? Does it represent any Gallente or Amarr battleships? At best, it’s representative of itself and maybe Ravens. And, you know, maybe kinda sorta flapjacksBarghests.
If you’re going to generalize about a group of ships that are actually fairly diverse, you can’t really go ‘oh, but THOSE aren’t representative’ because… well, no one or two ships represents the entire class. The Mael’s a very different critter from a Mega, which is very different thing than a Scorpion, which is very different from a Geddon…
If you’re building a battleship fleet, and you insist ‘YOU CAN ONLY USE ONE TYPE OF BATTLESHIP FOR THIS’… it better be pre-patch Machs. Cuz nothing else does everything.
Being slow as hell is the trade-off for being the ‘big’ subcapital ship, with the most tank and the most damage. There’s a pretty strong case to be made that we’re at a point of capital (and super-capital) proliferation where the line between ‘capital’ and ‘sub-capital’ in terms of ‘what might get dropped on your head’ has been completely wiped out, but that’s a much bigger issue than ‘how fast do I warp?’
And frankly, it should be tackled as a bigger issue—one of 'what the actual hell are these ships supposed to do, and do they do it?