After getting 5 pieces together of this set (some from weekly, some from the veteran Maw of Lorkhaj) I tested out the effect of having 5 pieces. Note that the 5-piece effect is extremely poorly explained, so I have "translated" it below as well as added a video to make the effect more obvious.
"When you use a synergy you create a lunar blessing for 10 seconds that grants a 2399 damage shield to nearby allies every 2 seconds."
What it actually means is:
"When you use a synergy you spawn a 12 meter (guesstimate) wide circle, lasting 10 seconds, that blesses up to 6 random allies with a 2399 damage shield that refreshes every 2 seconds for as long as they are standing in it."
Here is a video of the effect taking place:
https://www.youtube.com/watch?v=V-8eT1eeU2A
*The shields that people in the circle recieve are often invisible (the effect on you seems to vanish after 2 seconds, even if you still have the damage shield), but when you can see them they are blue shields similar to the Imperium set.
My personal opinion on this effect, and the reason for the title, is that for an endgame trial tank set the effect of having 5 pieces equipped is
EXTREMELY poor. The shield refreshes every 2 seconds, but
DOES NOT stack with itself, meaning it is just simply a 2.4k shield that keeps refreshing. This means you will rarely save someone's life with this effect, which ultimately makes the Imperium set that drops from veteran White-Gold Tower a way better set if you are looking for a set that grants allies damage shields. The Imperium set gives up to six players (yourself included) a 12k damage shield, and from my personal experience it has saved myself and other people countless times from dying to hard-hitting attacks, but the Lunar Bastion will likely only save you from dying to a dot (although most dots in vMoL are above 4k damage every 1-2 seconds, i.e. it is still not enough).
I think there are a few different ways it could be changed to make it viable for tanks:
A - the shield given to people in the circle is increased to 8k, or more, and still refreshes itself every 2 seconds you are in the circle.
B - the shield is kept at 2.4k but stacks with itself, and over the course of the 10 seconds you are in the circle builds up, ultimately resulting in a 12k shield to anyone who stood in it for the entire 10 seconds. Although this still wouldn't really save anyone from a dot or a hard hitting attack landed at the beginning of the circle's lifespan.
C - anyone inside the circle is granted a 12k shield, or more, that lasts for 10 seconds regardless of when they enter the circle, but the effect does not stack or refresh.
Sidenote: I wish trial sets would actually affect 12 people, you know a trial sized group. The whole nerf to the limit of shields granted by Imperium, the barrier ultimate and such, is really quite odd. Why does it have to be a limit of 6 players instead of the 12 it used to be. I mean we all know PvE is getting a hard time because a lot of changes are made to cater specifically to PvP. Anyway...
It is unlikely the set will actually be changed, which is a shame considering how cool the effect looks. Most tanks will still stick with the stuff they usually run when they realised how poor the effect is. I like the idea of having shields spawn on my friends, which is why I looked forward to this set, but it is simply a dumbed down version of the Imperium set that I'm running at the moment.
On a positive note, I do think the 5-piece synergy effect is really cool looking, especially when Twilight Remedy (golden glowing chest) and Moondancer (glowing arms or legs) have such subtle effects. I've yet to see what Alkosh looks like when triggered.
This is really just another set for the "failed to have any purpose" pile that a lot of sets in the game are tossed into. It may still be a decent 3 piece set, although I wouldn't run it. It is pretty sad since the Moondancer and Twilight Remedy are very nicely designed sets.
"Madness is a bitter mercy, perhaps, but a mercy nonetheless."
Fire and Ice