The Defence pack will take you down to RS gold level 1, but your total level of Attack Strength, Magic, and Ranged must be at least 10. This sounds extremely abusable. In essence, anyone who has max combat right now can transform into a pure maxed with 1 defence.
Facts: Each defense level is worth.25 fighting levels. Each defense level is worth 24.5 combat levels. Defense decreases melee, range and buy RuneScape gold magic by 10%. This stacks additively with damage reduction from tanks armour.