the only instance that winston should be used aggressively is when you have his ult. you can smack a whole team away from the point if you aren't discorded and then hooked by a roadhog while a bastion is shooting you or some stuff
not true
winston can be use aggressively on defense if the enemy team pushes too far and you have supports
if supports are exposed you can also go aggressive there
if you have a leap ready you can save it when you jump down from high ground then use it afterwards
harassing a mercy when she dies and when she gets out of spawn is the best thing you can do as a winston since her ult is the most value a team will have when they push
since she keeps dying she wont be able to be of much value
but as long as you can get a confirmed kill trade with a high value support such as mercy or lucio it is definitely worth it because theyll be left without a support, while your team probably still have their supports AND a tank (ie reinhardt)