I'll have to disagree.
There are moments when I just need to look at his pictures to cry but all of those involve death or the death of someone close to the character at hand. His most emotional scenes are a direct result of death.
I still don't think he NEEDS it, but it would help if he grew up a little bit and used it later on. Death can be a remarkably lame tool when you overuse it or use it when it's expected (Naruto) but if someone like Oda were to buckle up and use it well (like he's proven he can) it would be very effective.
If Oda ever does kill a Strawhat, it will be Luffy. He will never kill anyone else. He wouldn't do that to the individual character fans. That said, I doubt he will ever do that.
Without a doubt, the most emotional scenes in the manga for me were the death of Bellemerre, Hiruluk, and Rumba pirates.
Another worthy mention is Norland.
(I never like the flashback argument. Sure most deaths occur in a flashback but a death is a death. Rather its more like deaths occur in the flashbacks because those respective stories use it to be all that more powerful.)
These characters needed to die to have such an impact. Characters like Pell and Pagaya? No they didnt need to die because I doubt their deaths would have invoked nearly as strong as a response as those above. So keeping Pell and Pagaya alive were justifiable reasons and well something I personally prefer.