There are definitely improvements that could be made to blocking schemes. I'm not sure that it's as simple as "Have the OT block the DE lined up on him" though. In many zone run schemes the backside DE is left unblocked. The threat of a QB rollout or read/option is meant to slow down the end enough that he can't make a play on the runner. In many gap run schemes (power, counter, etc.) the tackle is meant to block down, with a FB, TE, backside guard, etc. meant to kick out the DE.
I do agree with you that pulling and lead blockers do not always execute their blocks though. Sometimes they don't block the player they should. Sometimes the timing of the play is bad with the blocker not getting to the spot ahead of the runner.
I play on varsity with sliders, in an online dynasty with 1 other user so most games are against CPU. I generally am happy with the gameplay, but run blocking issues are still an occasional frustration.