Nothing wrong with mining card in sg context..
In sg for it to be profitable (used to) at sg kwh and ambients you can't run it at 100% TDP. Depending on what's mined 70% TDP or less is likely. For the same reason apart from Turing launch, SG KWh is already not sustainable for the important CUDA miners with negative return quite recently. In other words, the moment those rigs go online money is lost even when you account for the crypto balance that's not yet sold. Main reason why trucks of 1080 Ti's are appearing on resale market.
And 10 series cards have locked voltages and power limits abit past 1.06v, to won't work without nvidia signed vbios. Current AMD cards on the other hand do accept custom bioses. Gets a lot murkier with the tweaks you're able to do.
Just look at the physical condition of the card. Otherwise, I'd only be concerned with getting used mining cards sourced from regions with cheap/free electricity. That aside, look at the VRM capability of the board. Iirc FE 1080 Ti PCB = Titan X(p) PCB. Also to kiv, FE PCB cards based on anaemic coolers already likely can't cool that much thermal load past stock TDP.
Only concern real concern in local context is just the fan bearing type, what's the rated operating hours its designed for plus board vrm design.