Leads + straights and/or flushes OTR is generally face up, the chance for him to have a better hand is high, even holding our 2P, Id probably fold, call is not that bad since he can also have only the A, the problem is that we block that argument with our A
The point is that this is face up most of the times, bluff is not expected more than value with better hands...
Raise more preflop, our principal source by raising the limper is the frequency he gives up postflop, so we can be winning bigger pots by adding 2 more bb pre, we also find bigger pots when we hit the board.