Why decouple when there are no "innocents aboard" any longer? The only time we hear there would be tactical advantage to not having the saucer is Worf's sales pitch in "Heart of Glory". But conventional wisdom seems to go against going to battle in two pieces - it's a special maneuver reserved for confusing the Borg.
That doesn't mean Keogh wouldn't have commanded the battle from his Battle Bridge, of course.
the Jem'Hadar ships engaged them in battle too quickly on the other side of the wormhole
That's a bit unlikely, because the system at which the battle took place must have been several lightyears away from the wormhole; the
Odyssey and the runabouts would first have to emerge from the 'hole at impulse, then go to warp, fly to the target system, and then reach Nog and Jake's runabout. It's only after this that the Jem'Hadar respond!
We don't know exactly how far or near this system was to the wormhole's Gamma end. In the pilot episode, "the nearest system" according to Sisko's runabout computer is Idran, which never appears again in the show; possibly it never appeared, period, and was merely the nearest system the computer recognized, said device being unable to recognize the system the heroes and the wormhole mouth were
in, or any of the other systems nearby. (And yes, the wormhole
is inside some system or another, as in "Destiny" we see there's a star there that creates a nice long tail for a comet...)
Several systems are within very short runabout hop... In "Whispers", the Paradan system can be reached within one hour and 14 minutes at maximum runabout warp (which supposedly doesn't exceed or even match warp five). But in "Battle Lines", there's a planet just 0.35 lightyears from where our heroes took Kai Opaka to sightsee - and it wouldn't make much sense for them to warp for several hours into the middle of nowhere when they were intent on turning back and taking Opaka safely and swiftly home all along...
So much for astrography lessons, though - we have no real idea how far away the planet of "The Jem'Hadar" was from the wormhole mouth. In theory, it might be
really far out in the sticks, with Keogh taking the runabouts within his warp field for some warp 9.2 travel, to cover in minutes what initially took Sisko, Quark and the boys several days at warp five or less.
Timo Saloniemi