I did the math here
. While you're tanking a target, you're going to see ~14.6% Absorb from Energy Blast and 1.73% from Power Screen, which is 16.33%. The 17% is a *slight* overestimation but that math was done while ignoring the fact that HS has a *substantially* better proc rate than the other attacks do because it's a larger number of attacks (68% compared to 15%) because I couldn't find a decent weighted use chance. If you factor that in, 17% is about right.
This was originally going to be an edit, but Kitru responded so fast. The gist of this post is, 16.33% or 17% sounds right based upon my parses but I think the results of one guy (me) and the model of one guy (Kitru) need to be corroborated by other Vanguards/PTs.
Looking at two recent HM SNV
and HM TFB
runs (ignoring ops chief, olok, and the horror; I should have ignored OP IX but I didn't), I saw heat blast uptimes between 47% on Dash'rode and 30% on operator IX. If I assume that my downtime was equally split between a state of +0 absorb, +1 absorb, +2 absorb, and +3 absorb, then I get values slightly lower than +17
11.7966101695 OP IX
which is an average of 13.31% or 13.23% when the fights are weighted by time...
BUT all fights have many factors that contribute to a decrease in functinal eblast uptime: the time at the beginning of a fight while eblast cannot be put on cooldown, button-pushing, forced running out of melee range, time that the other tank has aggro, and plain old waiting time. My assumption of a perfect 25% split between all states of non-heat blast absorb stacks (+0/1/2/3) is also not a good assumption; it's probably weighted heavily toward +2 and +3 absorb. This calculation also assumes that it's not possible to have the +25% eblast and +absorb stacks, which IIRC is wrong. I will check. Edit: yeah, you can build stacks while eblast is still up.
So based upon my parses, I have to agree that +16 or 17% absorb from heat blast-related effects when tanking the boss is reasonable. But I still do think other Vanguards/Powertechs need to chime in to confirm that they are seeing similar results. If people don't want to open up a spreadsheet editor but do still want to check their logs, a general rule for calculating uptime is (6*eblast count)/(minutes*60 +sec) should be between 0.35 and 0.45; if not, then either playstyle or this 16/17% estimation needs refinement.