With a capable crew as Voyager, it would have fared better in most fights.
Long term survivability is another issue, I don't think it was intended for extended-service and its science capabilites are limited compared to others, though its much smaller crew would in turn need less supplies etc.
The Defiant would have beat the crap out of the Kazon as soon as it got to the Delta Quadrant with its Rapid Phaser fire, Quantum Torpedoes and Ablative armour.
Buuuuut I seriosuly doubt It EVER would have made it back to the Alpha Quadrant. It would be at a big disadvantage being lost without any science labs or astometrics.
Its much slower than Voyager so the trip home would be a lot longer.
It wuldnt make it past Borg space simply because you cant outfight the borg. You either have to run real fast or use your brains and research facilities to get around them. Voyager was said to be the Fastest and Smartest ship, and had the right crew to use those things.
But On the plus side the Defiant's cloaking device would allow it to avoid a lot of danger. And after a couple of fights people would know they dnt wanna mess with that ship without some serious back up.