If you want a set then guthan is the ebst defensive. If you are like me and are bothered abut how good it is and not the looks then the following items mixed are the best.
Helm: Guthan, torag and verac's helm all give similar bonuses.
Body: Guthan, torag and veracs helm (again) all similar bonuses.
Weapon: Abysal whip.
Sheild: Rune kite, I guess.
Legs: Dragon plate legs.
Boots: Runite boots.
Gloves: Leather (give bonus) for look wear coloured though
Cape: Legends.
Amulet: Amulet of glory.
Ring: Ring of wealth, most likely.
You dont gain any special bonuses but it's the best defense armour mixed.
~Demon