I dont know about near lockdown defender, but he definitely has the potential to be an above average defender.
Thats true on last game. Sooner or later he will realize for the team to go far into playoffs and finals, he need to lead by example in playing the D. When things get serious, late into the season, he wouldnt have any choice but to play defense. I guess, all younger players (franchise) goes thru that process. Harden's D is not the only problem, we have so many other holes that need patching. TT, O, D bench, rotations, chemistry.
He definitely can be because was decent back at OKC. I think he may have to prob sacrifice a bit on the offensive end though. Only a handful of players can dominate on both ends of the court. I think D12 should pick up the offensive slack.