You missed my point. (I'm not an alchemist, i use mirror myself)
Trinket uptime is unimportant, % of viable uptime is.
It's not 16.7% uptime, it's how much of that 16.7% falls under eclipse where it has a use?
You can't calculate a mastery proc for boomkins the same as a dps class that has static damage increasing masteries.
If i look at a random log of myself, there's 16.9% uptime, 80% of the first proc in eclipse, 20% of second proc and 70% of 3rd proc fall under eclipse. Very random factors, 34 seconds of uptime during eclipse falls at more like 11% effective uptime rather than 16.9%.
(I rounded some numbers, you get the general picture though).