This is just my personal observation about the way Vespa is designing their contents recently. The first thing I notice is the lack of nerf in heroes these days, yes there are indirect nerf such as Warrior tough nerf, atk speed soft cap lowered or unintentional ones that they want to change heroes but make them weaker somehow, but there isn't a case that it is a direct named hero nerf in recent patch notes. Now let's move to the content part:

• Labyrinth: This content has been known for requiring specific team and heroes for each challenge. However the buff / debuff change each month make that even the specific hero for that may not be safe all the time. For example Assassin lab is known best for for Mediana cheese with her S1 and S3. The newest change makes you can't receive buff which void the strat while also add physic damage resist as extra salt to the wound.
• CR solo ban: The first CR solo is less subtle about it, but Satria is full out obvious with Mitra, Gladi, Annette, Mediana etc all getting the hammer. I managed to crawl my way through with DPS Kasel of all thing but boy it was suffering.
• Lizard CR: The ban to Mechanic is just one part of the picture. Aside from locking out Mitra obviously (something something best physic DPS), it also removes Crow and Rodina out of the play ground. Furthermore, coupled with the boss anti-melee mechanic, Roi and Gladi also have to bite the dust in this CR. Of course, physic team is still possible, but that would mean the need to use Requina and Selene (who is among the less popular main DPS option imo unless you are into her as waifu). Also the need for heal reduction calls for heroes like Dimael, Morrah or maybe even Maria (people usually don't expect her for end game PvE content at this point)
• Guild Conquest Boss 1: Magic team being meh compared to Physic? Aisha being phased out as a main magic DPS? Fret not, Tyrfas is here at your service. Requiring magic hits in huge number to stop his avalanche makes Aisha one of the best DPS slot here imo due to her multi-hits nature (S3 alone with all proc from S4 and UW can reach up to 60-70 hits).
• Guild Conquest Boss 2: This one also seems to favor AoE DPS (the breath lasts up to 15s from description and close to impossible to survive unless you kill the adds which then knock him down). This has also been hinted with Cleo UT and recent AoE heroes buffed such as Nyx, Lorraine etc.

etc etc

As we can see here, as amazing as Mitra is for late content long battle, he has been "conveniently" gimped to become not optimal for a lot of recent contents. On the other hands most them cater around magic and even AoE, making someone like Cleo become a valuable asset to have (despite all the meme around her). Also Shea gets like all the benefits with recent updates

Conclusion / TL ; DR: Vespa now instead of nerfing obvious strong heroes and cause rages to community, they decide to go a more sneaky of way of "This look like a job for Aquaman" by creating contents with more specific requirements that counter more popular heroes while allowing more niche heroes to shine. This basically encourage player to raise as many heroes as possible if you want to maximize your performance in those areas, so I am kinda curious about community reaction toward this trend.

Personally I'm on neutral ground, on one hand I'm all for encouraging more variety of heroes instead of having to see Gladi / Annette etc in everything all days, on the other hand I love Theo with all my heart and recent trend hurts him a lot as well.