This applies to unranked conquest as ranked is a bit on a different planet right now. I decided to post this after recent games with my friend (who is trying to get in to smite).
First, DO NOT ban Vulcan. Yes, he does seems scary, but believe me, if you have problems with Vulcan you are having even worse problems with other gods.
You always want to ban Hercules first. Why? Because he?s awesome babysitter for any carry (dps). He?s the perfect pubstomper and you want him out of the equation. He has one of the highest success ratio among the gods. You don?t want to have Herc (or his laning buddy) with 5-0 running around at 5min mark? Ban him.
Second god to ban should be Sobek or Ymir. They are the best available tanks in the game and you want one of them out of the way. I know how tempting it is to ban that ?omgwtfpwn? Loki or other damage god, but if there will be no Ymir/Sobek and Herc to babysit those squishy dps gods they are not gonna get fed (at least, not easily). If possible, ask your team if anyone is playing Ymir/Sobek and apply the correct ban.
Third option should be Thor/Vamana. They are the perfect bruisers, Thor is a godlike enabler and Vamana?s damage and sustain is legendary. They are valid bans, but only for more experienced players (when you know how to deal with Sobek/Ymir).
On the flip-side, if you feel lucky (or know people on the enemy?s team) you can try to ban a mid god (Agni, Anubis..) that can force them to go with ?unconventional? mid god and increase the chances for your mid teamplayer to win his lane.
So again, why you should ban sobek/ymir/herc as prio? Because they can produce perfect environment for their dps lane partner and they are compatible with almost any damage god. Gods like Odin, Hades, Guan and other pseudo-tanks are less threatening and have less tools to protect their partner.
There is another upside to forcing enemy to use sub-tanks, they may make mistake of going heavy tank builds on them and that is the best thing for you. In teamfights except for the small CC here and there you?ll be able to completely ignore them. Heavy tank build Guan or Hades will not be any threat to you damage wise. On the other hand, tanky Ymir or Sobek with just voidstone can be dangerous.
That?s it, there?s much more to it but I?m guessing this text reached it maximum length ? TLDR. My thoughts, my opinions. Not stating anything as definite fact.