Federation starships, at least in the 24th century, are relatively easy prey without their shields. The glass jaw of Starfleet. Ships like USS Defiant are designed to be able to survive being hit wthout their shields up, but most other starships are not.
Kind of contradicts the point in having a cloaking device, huh? The dumb writers of DS9 had to have their cake and eat it too. Lets forget everything that's established about ships having a cloaking device and do whatever we want. The Defiant had whatever it desired because it was the IT ship of the time. But when it was UPSTAGED by Enterprise E, Defiant had to look like every other vessel, getting their asses kicked, so the bad writer's new ship looked better.
USS Defiant wasn't designed with a cloaking device. It got one on loan from the Romulans so they could poke around the Gamma Quadrant for the Dominion. They could have put it only any ship, but Sisko wanted a ship that could survive longer than
USS Odyssey, a
Galaxy-class starship, did under Dominon fire. Federation shields were fairly useless against the Dominion at that time.
Defiant's weapons as a warship proved enough to destroy Dominion ships were a
Galaxy-class could not in the same amount of time. The cloak was to avoid having to fight while searching for the Founders. Otherwise you get the whole Dominion fleet chasing down one Federation starship, and even
Defiant can't take that much punishement. As it was, they still got captured, but made it farther due to the cloak and toughness of
USS Defiant.
USS Enterprise-D was still in service at that time.
Mind you in First Contact,
Defiant was taking far more punishment than any other ship in the fleet. Most ships seemed to explode as soon as the Borg fired on them.
Enterprise was even newer and supposedly designed for this sort of fight (much like
Defiant, but bigger) so its shields could take a hit from the Borg. Worf had likely been in teh thick of the fight the entire way from Typhon to Earth and
Defiant shows damage when we first see it, before it gets hit again by the Borg. It still was holding up under a Borg beam before
Enterprise saved it. Other starships we see under the same treatment blow up quickly.