Doing the unexpected, being unpredictable, is a formidable weapon in war. I think it is usually a mistake to say that one should never do this or that. Do what a situation calls for, however unconventional it might seem out of context.

I use archers to attack effectively, usually against other archers or ashigaru, or against the flanks or rear of any troops that are engaged with other troops. You can often affect an enemy unit's morale such that they flee with a well-timed and angled double-team.

Sasaki doesn't need to melee attack with archers because his mastery of tactics and control on this game's battlefield far exceed those of most Shogun MP players I've encountered. I can testify to this because I've battled against him many, many times (and lost, mostly). If you would like some lessons in frustration, meet him for 1v1 battles on the Fakeserver, or using the Samurai Wars mod for MTW.