You have to go back to one of the earlier weekly updates to find it ( it's a few weeks old ) but Deej and Bungie basically said that anyone within 5 levels of you would be more or less playing on an even playing field with you. What Iron Banner 2.0 does is it stops Lv.30 characters from being destroyed by Lv.20's and prevents Lv.1's up to Lv.19's from entering and being competitive.