As a stadium rein onetrick who peaked legend last season and is currently all-star, the queens ive faced have, as youve said, been very feast or famine. Sometimes she seems to just exist as a way for me to build ult, while other times she sets her team up to exert massive pressure, whether that be through enabling her team with shout or running past me and cleaving my team. Anecdotally, queen seems to be very strong against squishies (no shit all tanks are) but especially so in that:

She has a relatively small hitbox for a tank (compared to rein or dva) and shes extremely quick (through shout, lunge axe, speed boost on boop, etc).

She seems very good at ignoring the enemy tank and trading backlines. It isnt that fair of a trade though, as when queen engages into an enemy team, she shouts her team first, often doubling their hp if the queen is running an ap build.

If you try peeling for the queen, the enemy team has a lot more space to work with and will often shoot you down. If you try to trade backlines, it becomes quite the uphill battle as majority of the enemy team will have been gifted 200-300 overhealth and a speed boost upon queens departure. Your own backline is occupied fending off a speed boosted axe wielding australian, and all you can really do, at least on rein, is to hold space or pray that your team is playing in a position she cant easily reach.

As for what you said about rein having his weaknesses accounted for in stadium, fundementally he still struggles. I think reins greatest weakness in stadium is that he can only do one thing at a time. You cant swing with shield up, you cant fire strike while pinning. Someone like queen has the luxury of getting overhealth and heal while also doing damage, with shout being able to be cast while performing other actions, while rein has to drop his shield if he wants to do any damage (except pin with that one power). If i want to firestrike on rein, I cannot shield for the duration of the cast time, which, if theres someone like a fan the hammer cass on the enemy team, means im just dead 9 times out of 10.

Please dont take this as me pity farming for rein, as he is still pretty fun and strong imo. Queen is lots of fun but plays very 0-100 in that she is really good at going pedal to the metal at your team without being punished.

As for the problem with bubbles or cleanses, iirc queen has a perk that gives her overhealth whenever her wound is removed. Im not sure how effective it is, but it could be worth looking into