Lefties Bisharp is definitely a thing, as is dread plate/blackglasses, collectively making up about 44% of all Bisharp. As for BD Azu, his most common spread (the one recommend on the dex) can still be outsped using Quiet by investing just 8 EVs into speed, so that's a nonissue. You do end up taking a second hit from defensive Heatran, but of course Mega Venu shouldn't be your go-to guy to hit Heatran in the first place. Which is to say, Mega Venu will rarely be 1v1ing him (rather trying to surprise and nail it on the switch in), and most teams should have something else to deal with it anyway, so I don't see it as that much of a downside. Plus, if we're already talking in terms of minuscule/situational benefits, the added damage of a neutral over negative attack nature isn't completely useless, for example if Heatran or whatever you're using EQ for has prior damage a 2HKO can become an OHKO.Bisharp is still 2HKOed 100% of the time by Life Orb recoil by modest eq anyway. And running quiet gets you outsped by defensive heatran, which is nice to outspeed when you have EQ especially. Running quiet means you also mean you underspeed BD Azumarill, which can OHKO sometimes with +6 Play Rough after Stealth Rocks. Overall Quiet doesn't give anything notable, while modest gives somethings situationally useful, so modest would be better.
Overall this is a pointless and fruitless debate. If you or anyone want to use Modest, be my guest. I rarely run EQ on Venu anyway.