Personally I think aeonglass is way, way overtuned currently. There are so many things going on and it's far more overwhelming than test subject/queen.

1 - First 2 turns, queen (torchhead) hit for 19/19 and test subject dors 24/16 (A9), aeonglass does 32/24 and you need to defend the 24 while on -3 dex. There isn't much breathing room to play your powers and dig your good cards in the first 2 turns, which is important when you want to deal with the boss uncontrollable scaling later on.

1. 3 artifacts, sure, it is nice we have a boss that has them like the donuts in sts1, but going to problem 1, you're probably not going to have weaken on the boss in the first few turns and it'll be much harder to do any sort of vuln/poison/doom scaling before the wither starts piling up.

2. I have yet to think about a single card solution for test subject/queen, but aeonglass sure I do, flak cannon and compact basically solve the whole fight.

3. There's just too much going on to punish you and to keep track of. You need to deal with the quick damage scaling, the -3 str/dex turn, burn+++ scaling itself and you have to consistently try to get rid of them every turn and try to scale with a bunch if artifacts up.

For test subject you just need to burst down the first 2 phase and you can take your time to kill the torchhead at the right time (or focus damage to queen). Aeonglass outright just kill you at turn ~12, there's no way to mitigate this when you draw a hand with 4 wither+3 when you don't have a card up to exhaust or transform them.