Arguably people complaining about the YouPudding rush could be seen as thinking the Serjeant is OP at least in that context. Even apart from that, there are threads where people think it’s too strong:
I also remember a single post in a larger thread where someone thought Rathas were OP because of their Imp stats (i.e. matching up well vs. Elite Mangudai). But yeah, the majority of suggestions for those units have been for buffing them. Maybe flaming camels check the “never thought of as OP” box?