It essentially allows mesmer to swap weapon sets every 8 seconds. Taking into account the fact that many clone creating skills have very short cooldowns (Mirror blade, phase retreat, scepter and Oh sw block etc…) I think there could really be some potential here. Especially if we assume that we have traited for celerity and atleast one of our weapons.
On the other hand I could see it hurting dual energy sigil users as using them would become unreliable as you wouldnt always get the bonus endurance… Imo one energy sigil is enough, considering you get it now every 16s, not every 20. In theory, using this runeset would increase damage as well combat tactics/mobility/survivability.