This can be boosted. I just finished a successful session where 10 people got Penta Kills in about 45 minutes.
You'll also be able to get this achievement:
The Last Man Standing achievement in SMITE worth 35 pointsBe the only god left alive on either team in Conquest, Assault, or Arena.
1. Set up your session for a time that is early morning on a weekday in Australia. This is around 12pm PST, 3pm EST, 8pm GMT the day before the Australian weekday (so never make this session on Friday or Saturday). It's very hard to get matched up at any time, but this gives you the best chance. If you can't do it at these times, wait another day until you can.
2. Get 10 people. Split them into two parties with as close to an average level with each other as possible. All 30 is ideal, but far from necessary (we had 3/10). The game heavily weights your level when matchmaking, so having an even spread is key, but not so important you can't work with whatever you happen to get in your session.
3. The two party hosts need to select Australian servers. You do this by pressing X when you're choosing a gametype to search with your party.
4. Search together (one of the party leaders will have to join the XBL party of the other for the matchmaking portion - 10 people can't fit in a party together). Tell both parties NOT to accept until 15 seconds are left. That way you'll know you've found eachother.
5. If one team gets a match and the other does not, the other backs out of course. Everyone on the matched team should accept except ONE person. That one person will fail to accept and receive a 2 minute search penalty. Wait those two minutes and try again. On your next attempt, the team that found a match should search 10 seconds after the other team starts (the search gets wider as time goes on, so that team needed a wider net). If it fails again, a different person needs to not accept (if the same person does, they'll get a 5 minute penalty for a second offense) and you add another 10 seconds. Keep going until you find each other.
6. Once in the match, everyone should choose assassins or hunters. These have high damage potential and don't rely on cooldowns. Mages are frowned upon for this reason, though someone like Kukulkan is acceptable.
7. Level up to level 15 or so. You could skip this step, but I think it's worth it to make sure kills move swiftly (and ensure everyone gets Last Man Standing).
8. Everyone will meet in the jungle near the enemy base of the person getting the penta kills. When everyone is there, the killer begins the massacre and his team runs straight into the enemy fountain (which will kill them very quickly - the Phoenix is not fast enough). Everyone should die except the killer, and both achievements will unlock in-game.