Clarification about backtesting method/data

[overflaw]

Hello,

I wonder about one thing: let's say I got an MQ4 EA reasonably working on simple backtesting (Model : every tick). Considering the fact that my signals are generated by indicators and calculation made on past close candles (no matter the timeframe), I don't see the point about weakness around OCHL data only (versus complete ticks database). I'm using so far only direct Buy an Sell order, so AFAIS, SL and TP can be predicted this way

I'm a newbie, appreciate if someone could clarify this point for me, I probably miss some things.

Thanks !