Basically the best contributers to AW are the players that work on their full bench of 30 heroes the hardest, imho. That is the foundation, that is where your true contribution to the team sits, right there. Whether you pick easy targets or not, your potential is all determined by your bench.
How you employ that capacity, is just a nuance of how the final point distribution plays out: a bit more to you, or a bit more to others. Full one hit wipes are very efficient in terms of flags spent. Actually underdeveloped teams won’t put a dent in partly destroyed teams as well.
As long as you employ teams that are -suitable- in strength towards the target and the goal of your attack, you’re doing the best for your alliance. Suitable as in: not too weak (will probably fail) and not too strong (overkill is wasteful). So if you become best scorer because there was a good match between your bench and the available targets at the times you came in looking for some fights, then that’s just good play.
I have 6 teams that are capable (> 2.400 team strength). I’ll typically use 3 for full wipes, and the other 3 to either sweep up partly destroyed teams or to take out the center (and preferably more) to soften the target for others. Sometimes an intended softening up turns into a full wipe, or a full wipe turns into a mere softening up.
What you don’t want happening is a softening up turning into a botch: no hero kills. So sometimes you need to keep your powder dry because at that time there’s no suitable target.
Another point about timing: at what point in time of the war am I playing? Saving partly destroyed teams for others to “harvest” isn’t the smartest idea when there’s only a mere few hours left in the war and most others are spent. I have been known to “keep my powder dry” and tip the scales even more in our favour near war’s ending.