Sharpshooter is useful if you Nex, reverence for lots of things that require staying power but saves only 10k per use, knock-out is the only one that increases melee kph but only slightly, surefooted doesn't work beyond 93 agility, call of the sea doesn't seem to do very much, oddball is fun to watch?
Reverence is arguably just as good at Nex, for the very reason you just said. For RSOF teams, Reverence is generally better, as the purpose is to deal the minimum damage needed to remain on the team, while staying as long as you can so that you aren't forced to teleport prematurely. In teams where loot is actually shared, it depends heavily on how experienced your team is. Teams that are coordinated to bank, restock, and return quickly benefit more from the increased kill speed, while teams that spend a significant amount of time banking are better off prolonging their trip by a kill whenever possible. Also, members with better gear benefit from Reverence more, as later in the trip, they will be using their Super restores primarily for prayer and not so much for stat restoration (I have personally gone through several 4-man and 5-man kills using one Saradomin brew or less, usually just to heal off Overload damage.) In contrast, someone constantly using Saradomin brew will find themselves using a lot of Super restore anyways and losing their excess prayer to Nex's draining tactics.
As far as which aura to buy now, I would make a list of the ones you like most. Then purchase the one with the most expensive normal price, assuming you don't need them soon. By buying the more expensive one now, and the cheaper one after, you will have more points remaining than if you did it the other way around - points that can be saved for future possible upgrades, other auras you may decide you want after all, or emotes/titles.