I personally use both. (I have 3 health and energy sigils, which doesn't necessary make a difference)
For solo I would use boost, get my shield up and hammer away, if energy starts running low I would sacri, usually when eshield is almost ready for recast, then my eshield would most likely break 2-5 seconds before its ready for recast, I would take a few hits, then bam eshield up again. With this boost-eshield-sacri energy shuffle I almost NEVER stopped fighting (unless I have other stuff to do, like chat, trade, etc), only stopping for a few sec bc I recast boost or shield, or simply wait for cooldown of my skills.
The benefit of having sacri here is if ur shield happen to break before another one is ready (usually when fighting a 3* 4* mob), and you need energy (eboost is virutally impossible due to interrupts), or you don't have enough energy to bring up ur eshield, you can do some self-mutilitations to bring energy back up, I hope you at least have a health regen of some kind b/c it would be really helpful, regen ur health from previous sacri's while shield takes all dmg.
For group I would do the same thing, the advantage is I have a team (duh), which speeds stuff up faster, meaning less pressure for your eshield
. Well, you can then use the spare healths in ur eshield to sacri on ur team members to regen their energy, reducing down time.
The benefit of having sacri here is if your team members do not have a regen (or enough regens), you can help them regen their energy. I personally (when I was lvl 50) killed a defector guy (believe it was the one at greygorge leystone, can't remember his name) with a lvl 40-ish ranger with NO regens with this method (WITHOUT DYING), well, by kiting of course, but he have NO regens of ANY kind (b/c of the defector's proc stance and the ranger's low lvl, I was the main dps, meaning he have complete aggro on me, no pressure for the ranger
, and he kept him bolased, haha can't scratch me, and even if he did, eshield
Well, my 2 cents, use both :p.