Full torags and a dragonfire shield (full), amulet of fury, dragon boots, Skillcape (t) and a combat bracelet offer the best melee defensive stats though if you replace the torag's chest and legs with bandos you get the best range def.
As the difference is marginal and torags is by far cheaper it is usually the armor of choice though they are often seen in more flashy gear, maybe not with the best stats but gear meant to show off their high levels or wealth.
In F2P the best armor is full rune with a chain and kiteshield.
In terms of offense, most defense "pures" (Also known as tanks) favor a bone dagger (P++) because of the poison damage it can deal as well as being slightly more accurate than a iron dagger. One of the runecrafting talisman staffs offer the best strength bonus in both F2P and members though a red topaz machete is more accurate, but only has one third of the strength.