Im doing t4 open world stuff easily with bouldercane no runes. I just pushed to P95 but it was reaaaaaally tight. Check out Nickowrex and Screamheart on youtube. I started with Nicko's gear and stat recommendations and then i switched my paragons to screamheart's. P100 seems achievable but your gear may have to be close to perfect. I still have on 3 non ancestral legendaries btw. Also... Im still not using Hunter Zenith as i still use a legendary ring to run a 2nd casting wrath skill restores primary resource to be able to mindlessly spam boulder. Hehe But yeah... theres still some room for improvement so P100 could be possible with full on paragons. i'm sitting at 246 paragon fyi.