I'm thinking about what I want to play at the next Austin Vintage event, and Storm is hard to pass up. I've noticed that most recent Storm lists on Mtgtop8 are playing 4 Dark Petition, and splashing for Mentor. Is this pretty much accepted as stock at this point? I'm currently on 3 Petition, no Mentor.
I haven't played Storm recently (as in, past 3 months or so) but I don't think this would be accurate. As mentioned above I tried Mentor and didn't like it either. I actually preferred doing it the Tinker route as an alternate win condition, with Tendrils being the primary plan. It's worth noting that keeping the colour splashing to a minimum does lead to a more stable mana base, being able to just fetch up a bunch of basics in the face of Wastelands is highly underrated.