My team consists of mostly level 25/26 Tyrants. 24 Smilonemys and 23 Gemini. All of them very lightly boosted, like 1-1-1, 1-2-1 or so (some, even less, like 0-0-1). I can say, if my Gemini was at 26, it would not be as strong as Maxima and Indo G2, but not too far from them. At 23, it is really far from unbeatable.
I do face very few Gemini, like, it’s really rare. Maybe some folks own it but at low levels like 21/23, so they are benched. So it doesn’t seem OP. Indo G2 is OP, some people with stronger creatures have one at level 22/23 and it is still really hard to beat.
Of course, if you boost it to heaven, it will be OP. But then, about anything is OP if OB. Even low apex creatures can be OP if OB. So, to say an OB creature is OP… I would say the problem are the boosts, not OP creatures.