I thought it was unrealistic within the confines of the universe they created.
A Starfleet ground war would have personal shields (seen them), phasers that can stop an approaching force on wide angle settings (seen them), and many other things that, really, would make a ground war pretty obsolete.
I just couldn't wrap my head around the logistics of the episode. Seems like they just wanted the typical war episode for no other reason than to have one, and forced the circumstances in the story to get one in a way that wasn't true to the universe Trek had created.
I've been thinking about this for a while - for me, one of the most interesting things about personnel combat in DS9 is that phasors no longer vaporize people when they are set on maximum - what's changed?
I wonder if the weapon is far more deadly, or rather, has a more powerful "yield," so to speak, when it is set not to vaporize but to channel all the energy into one spot - in AR-558 starfleet is using the same phasor rifles that turned people into nothing on TNG, so why are they not doing the same thing here?
My theory is this: That starfleet uniforms are actually quite tough when it comes to weapons fire - perhaps they deflect or redistribute the energy. I imagine that Jem Hadar armor must also be something quite hard to punch through. Perhaps the vaporize settings are ineffective against armor.