I'd agree to disagree if you simply mean that both are broken, which they are to varrying degrees, and I might agree with you about echo as well since the problem is with the actual units ST specials spawn rather than the specials themselves (which I could see being a legitimate design limiting factor).Echo is not a bigger problem than defenders. Hell without justice I would argue that echo is fine now. Defenders on the other hand are basically mandatory. Broken combos in just about every faction. Purify is currently a garbage counter due to very limited options. Go look at Northern Realms options for purify as case and point.
I hope I understand you right and that you're not on the other hand insinuating that ST isn't a big problem this meta, specifically dwarve since echo is just their best synergy. Dwarves being broken is just a fact. Most of the relevant PTR testers and competitive players have voiced that and the nerf is basically inevitable. It's just a question of when and one in a series of quality assurance shortcomings above all but that's a topic for another thread. My biggest worry is that they'll axe echo and not even touch dwarves but at this point I wouldn't really be surprised.
As for purifies you can literally run a 4/5p neutral tech that turns a defender into a point play against 5/6 factions. And if you're playing NR this month you shouldn't even be teching purify, you should just play Calanthe with the defender and finally play engines that stick throughout the whole round.
I've tried not even running defenders and a single purifier and I have a pretty satisfying win rate. Pretty sure 70% of my losses were to dwarves.