As far as I can tell from the description, it doesn’t stack. Why did a couple of guides say I should ‘spam it’ under certain conditions when able. EX: heroism, etc.
to avoid capping energy.
normally you want to stay above 50% energy, and let the auto attacks with the envenom buff do their thing. the goal is to maintain the buff, not keep it at max duration, or you run the risk of starving yourself of precious energy.
have you heard the term ‘pooling energy’?
rogues used to- and still do- have periods of downtime where they simply wait for their energy to get close to full in order to take advantage of a window of opportunity for more dps.
however…
capping energy too often is also bad. at that point, spamming envenom is totally acceptible, as the only reason you wouldn’t is to not starve yourself of energy. if you’re overflowing energy, spam away!
Envenom does not ‘stack’ but it does benefit from pandemic mechanics which will increase its duration up to 25% more time.
Your passive, Cut to the Chase, extends the time on SnD which is integral to your damage.
There are a few talents that also benefit from using it and specifically when you have already gotten the buff (Rapid Injection: 10% damage boost while under the effect of Envenom) and buffs your other abilities after you use it (Dashing Scoundrel: Increases poison crit, Poison Bomb: chance to deal additional AoE damage)
You cannot spam it like other classes would just button mash, since you need to build up points. The only reason you would not be using this ability is if you are low on energy (hero/BL dramatically increases energy regen since its tied to haste) or need to reapply Rupture.