Yup! I consider Enforcers, Hammerheads, and Sunders all good ships in AI hands (though enforcers are a bit slow for early game) that I take rather than cruisers. Destroyers for me are a high offense usage of DP with "good enough" mobility to either avoid or swarm enemy capital ships and heavy cruisers, while keeping busy/killing all the smaller things themselves. They are tough enough to take limited capital fire and numerous enough to not get swarmed by frigates. In terms of range, they actually have much longer range than frigates. I'd expect a basic "mid range" hammerhead (mortars and railguns) to have 840 range, while a long ranged one has a mixture of 1200 and 840 range weapons (officers boost that up to 25% of course). A midrange sunder has 840 range, while a long range HIL build has 1200-1400 (before officer if applicable). Both of them have damage systems as well.
In terms of if I'd take a destroyer over a "high performance" frigate like a Hyperion/Scarab/phase: it really depends on my fleet/skill build. If I can afford to go into both tech and leadership enough for wolfpack, more officers, additional flux (and phase skill for the phase ones), and if I train up an officer with the right skills, then I think those frigates can usually do better. Often times I don't want those skills, or want my officers for different ships (or haven't trained them), or if I need the ships to escort capitals, or if I want to engage a station, then I would want destroyers. One way I build has officered frigates as my hunters, officered capitals as the anchors, and unofficered destroyers as the "infantry", where in effect I'm choosing both high performance frigates and destroyers, only the destroyers don't need any skill or officer investment to be valuable ships.
In terms of comparison to cruisers, I would take 2 Enforcers over 1 Eradicator, or 2 Sunders over a Champion in most situations just because the destroyers bring more bang for the DP buck. I think that Herons have a niche as the fastest carriers and Gryphons have a niche as missile spammers (though conquests nearly do the job as well per DP while being more officer efficient and also bringing serious gun power). Destroyers tend to have less defenses than cruisers per DP, but they also take less damage and are more mobile, and with numbers comes serial venting, so I don't really see them dying much more either. They also tend to be a lot cheaper!
While I see a niche for destroyers, I don't see one for cruisers: if I'm taking a slow cruiser that can't get away from an enemy swarm effectively, why not take a capital? To me they fill the same role, but better. Like the Dominator: I like the Dominator as a ship and feel it's not in a bad place power wise... but if I'm bringing a Dominator, I can afford to bring an Onslaught and do the job better. Same for Conquests obsoleting a bunch of the speedier/missile heavy cruisers. So I tend to gravitate towards ~3 capitals, leaving 5-7 officers (possibly + AI cores) free for smaller ship classes. Cruisers don't make the cut in terms of providing either numbers or efficient firepower. They are too much of an investment to serve as an escort, but are vulnerable to swarming so can't really operate independently either.
I think if I liked capitals less, I could see myself running a wide cruiser fleet (say 8 officered cruisers + a supporting frigate contingent). There is a stage of the game though (say taking a ~100DP fleet up against the first capital ships or against a luddic path swarm) where I'd be apprehensive about using just 1 or 2 cruisers (unless I got lucky and found like a Doom or Aurora for me to pilot). The whole "too slow to run, too weak to fight" thing.
For endgame, the main consideration is Radiants, as they are the only enemy that can catch and pop a destroyer fast. Thats mainly a case of where I need to be on the ball in terms of my orders: holding back the destroyers until I've let the capitals engage the radiants first and then letting them move in and flank when the radiants are fluxed up some. I'd expect an unofficered destroyer to be able to hold off an alpha core AI destroyer, and an officered destroyer to be able to hold off an alpha core brilliant - though a burst of missiles can swing both those fights in either direction based on situation.
In terms of builds: the classic HIL Sunder with 2 gravitons (or 1 graviton + 1 ion), the mid ranged Hammerhead Mortars + railguns (or the mixed Mortar + Arbalest + railgun + light assault gun), the long ranged Hammerhead (HVD's + railguns), and either a mid ranged assault enforcer (Heavy needler + 2 heavy mortars), and the long ranged escort Enforcer (HVD's + flaks, harpoons instead of reapers), all just work. You can throw them into nearly any fleet and get value out of them in any stage of the game.
Yeesh that turned long!