I agree that it SEEMS like it triggers way more than it should. I've told my guild that they should seriously find a spot for this astral if they get the orange version, just on the sheer amount it seems to trigger. It can turn a battle right around if it triggers once or twice or even more. That said, there is a key factor you need to take into consideration here:
Judge by the attacks, not the number of rounds. Skills like multishot and any AOEs hit more than once. Every "part" of these attacks is treated as individual by the astral and each has a chance of being dodged.
If you're fighting in Group Arena, it can skew things in a deceptive manner because of the above. If an archer uses lunatic fire, that's 3 attacks per character. If there are 3 characters alive on the other team, that's a total of 9 chances for that dodge to trigger, assuming each one has that astral equipped. Therefore, you will often see multiple dodges out of that and it makes it seem like it's triggering too often in that case. Situations like these may be giving us the illusion (pun completely intended) of this astral triggering more than it should. In a 1v1 environment, things look much more like they should, in my opinion.
I think you got unlucky Sith. I dueled a guild member earlier, and he beat me because it triggered twice for him. His was at 10%. I had mine equipped at 8% and didn't get a single dodge out of it. That said, I won a fight in GA today because it triggered twice in a row for me. However, more times than not, I don't get it to trigger a single time in GA fights. It really is all about luck, and when it happens to be a case of very bad luck for you like you stated in your example, it's very easy to think something isn't right, but I can tell you from experience that over the long run, it definitely seems to be triggering at the right rate. It's still a wonderful astral to have.. you can win fights using it that you otherwise wouldn't win if you just happen to get lucky, it's a lifesaver.