I've been able to test, and the power dragon is a much better over all unit than the energy cannon. I didn't expect it to be, but the power dragon really surprised me. The energy cannon is like the sentinel, can beat all defenses but takes some damage, and because the other units are better compared to SAM the energy cannon takes more damage than the sentinels did vs SAM units. I can fight most GBG combos with power dragons taking very little damage, with 1 or 2 fights that are a bit tougher, but still very possible until very high attrition (4 ranged + 4 fast, for example).I don't know that I'd say it's a great unit. Granted I can't actually test them til they hit live, but the Energy Cannon already seemed better to me.
Power Shot is somewhat overrated imo - though they did add some of the few reasons for it to exist to this age (reactive armor, stealth, flying).
With the reactive armor only being 4 though, a high AO & Keen Eye can overcome that well enough with any unit. Furthermore with low base attack against a high base defense and with a bunch of boost in the picture, it might not hit for more than 4 very often anyways.
The stealth unit may not be able to make it to a tile it can hide on having the lowest initiative in the age.
Flying normally only matters to the artillery anyways - so in that sense, it just makes the fast unit flying-in-name-only for the age. But since the fast unit still moves first it should still win the matchup.
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In terms of the nerf, it's disappointing - doesn't change my evaluation of the age that much - still likely a boring but safe combat age where at low-medium attrition any unit can beat any unit. Medium-high attrition is a bit sketchier unless you have a focus on defense over attack since the units mostly skew that way.
Playing with the damage calculator it seems at the sort of attrition that I actually worry about how things work, this nerf took PD vs SF damage from 3-5 to 2-5. So not the end of the world. They were already going to be reliant on crits/keen eye procs and range to win those fights.
I do have high attack boosts, but I was able to do all but 1 GE encounter with 1 power dragon + 7 rogues (couldn't beat 8 fast + 7 heavy, 1 ranged), only losing 2 power dragons on the way. I have no doubt I could beat all with 8 energy cannons as well, but would definitely have had more losses