I had some sympathy for them from the start. Maybe the combat aspect wasn't portrayed well, but Gul Macet's ship, the Galor Class Trager seemed little match for Enterprise. Macet seemed like a man willing to go down for his people despite the chances of winning, and whatever the class of the military vessel the Phoenix destroyed, it didn't seemed like much of a fight either; though we should remember the Nebula Class is an extremely powerful ship. Overall I got the impression that for whatever reptilian reasons, the Cardassians fought mismatched border wars with the Federation previously, but like with the Talarians, people died on both sides.
That the Federation was in no place to fight another war with them at the moment seemed less about them than the Federation's being spread too thin for other reasons* - no need to pick a fight they'd win, but at higher a cost than they'd like.
The Galors seemed weaker ships in "The Wounded," like midsize ships - maybe why they often came in pairs. Then in "Ensign Ro" Riker called them "top of the line." Probably because they didn't have other physical models for the Cardassians, but, ok, maybe I don't buy them as Galaxy Class strong, but they're being re-presented as stronger than last time. And that, they travel in multiples says something scarily reptilian about them.
I did find it problematic in Preemptive Strike when Evek's ship was taken out by fighters (was this the end of the battleship era and the beginning of a carrier one in Trek?), but they were equipped with larger ship weapons, whatever consolation that was.
That they were impoverished I think was supposed to liken them to Germany after WWI. Though if you think about it, it would take a lot to combat the wealthy Federation, I didn't hold their poverty alone as reason to underestimate their destructive capacity, if they really put their considerable minds to it.
I think DS9 presented them as more dangerous, given that they were the main power in the area. Certainly the were trouble for the Bajorans and others, and in their own literature and minds they were main powers, but even there, the Klingons almost conquered them entirely and they only gained new predominance through the Dominion.
*They beat back the Cardassins in multiple "border wars", the Talarians in a war, we later find out the Tzenkethi too, had recently expanded their number of memberworlds by many (per Admiral Quinn in "Conspiracy"), and had new baddies in the Ferengi and Jarada and others to worry about.