André Soares
First Post
Where Portent shines is when an ally needs a very high roll to succeed, or when an enemy needs a very bad roll to fail. That doesn't happen too often, but when it does, you can nail it--if you have a suitable Portent roll to give out. Like I said, if you roll a 10 or 11, it's not going to do much for you that day. (Which is a nice bit of flavor for the diviner, incidentally. If you get mediocre results on your Portent dice, you can announce that you have seen leaves falling from the tree still green, and smelled smoke on the wind at dawn, and therefore today is an inauspicious day for your quest and it would be better to wait until tomorrow.)
It's also worth noting that there are things which can counteract Portent. Legendary Resistance is the biggie. Even if you force a natural 1 on the save, a shot of LR will turn that failure into a success.
Portent is a very, very good ability. It was absolutely my reason for picking diviner last time I played a wizard, and I do not regret that choice one bit. Effectiveness aside, it's just fun to point at the DM and say "You roll a 2." But I would not call it earth-shattering.
10 or 11 are great for death saving throws.