Guild Wars 2

If I place all six facets (including F2) on myself, how long do they last before needing to be refreshed? And how close do I have to be to someone for them to benefit from them? And finally, should I ever consume them while grouping with others?

You cannot use them all at once, the elite alone needs 5 upkeep, F2 has another 2 and once you hit 10 upkeep you cannot activate any more. As such, you have a net drain of -5 energy per second, meaning you can keep them running for 10 seconds before you’re out if you start at 50% energy after swapping legends or 20 seconds if you start at 100%, obviously.

Radius should be 600 units, as you can check on the wiki.

Consuming is usually only advised (in PvE) on F2 if you don’t need the boon duration buff (i.e. no Chronomancer in the party) and the Swiftness one for some extra damage. Otherwise just swap legends when you run out of energy, swap back and use them again.

Any 1 facet you can keep up indefinitely. They don’t time out on their own unless you swap stances or run out of energy.

All but the might facet can be situationaly useful to consume although only swiftness is one I’d recomend consuming any old time you want more DPS.
-Might stacks vuln on the targets but thats really easy to do with sword anyway and only slightly slower. normaly not worth puting it on CD
-swiftness has a good AOE on consume and its prety common to have a long duration swiftness boon up if you are in a group or had it up between fights.
-Consumeing the heal can be amazing if you know a big hit is comeing in. If you’ve been takeing attrition damage and are geting low feel free to consume it and take a big attack on the chin instead of dodgeing, it can heal you to full.
-Furry facet is a stunbreak when consumed so use that as needed, the blind and stealth detect are normaly not worth it.
-eliet is a prety heafty knockback but is also on a long CD. Its also so expensive to maintain that I rarely use it for its buff unless the other buffs are not needed. Most of the time I just use it as an interupt.

I normaly wouldnt consume F2 unless you really need to turn it off right away and dont have time to let energy drain shut it off for you. A good example would be if you need to use assasin stances quickness buff as you cant turn it on with F2 active. If you really need a few seconds of every buff and cant/wont swap to dragon to get them that way then go ahead and consume.