I wouldn’t say that OnS is the best pound for pound guild right now. I’ve seen them get beat by Jekz multiple times in not only open field but in roster vs roster fights. Most of the time it looks like OnS has at least 5 more than Jekz also. So I would put Jekz above OnS. Also Jekz is Rekz just a reform with a different driver. At least they didn’t go and stack other guilds like KEK and BORP.
TM should be on the list also Team Micro that is. They were good back in the day and from what I hear are just getting use to the meta right now.
The most legendary guilds in NA would have to be Agg, NS, EP. Those three guilds were the best in the game for the longest time and stood the test of time until the game got boring because Anet neglected to do anything for WvW.
So basically the best guilds right now in game would be KEK, BORP, Jekz, OnS, vX, TM (Team Micro), and maybe Mada (which helps out KEK in gvgs).
Most other guilds run more than 20-25 so they don’t really deserve a shout out.