Her shield stance makes her able to absorb a lot of your basics, which this build is based around. Try to avoid her if you can.
Athena's preemptive strike becomes quite the problem if she is able to stack it up, negating basic attack damage again.
So, you want to play Bakasura. Let me tell you something first: you want one v ones. If you go in alone against more than one other god, you are probably going to die. However, if you go against someone who is alone, and you hit your basics (preferably with butcher blades active) you are likely to win. So, hit your basics, and one v one them.
As Baka, you want butcher blades on often, and you want the damage from them to proc even more often. So, you want to attack fast. The more hits you get, the more true damage you get. True damage isn't mitigated, so you're doing at least 70 damage per basic with butcher blades active. But, you need to be in melee range to hit your target, which brings us to the next topic...
The frostana (formerly frostalis) combo is one that has existed for a while, rest in peace hastened fatalis. It makes landing your basic attacks continuously very easy because while you don't suffer a movement speed drop when you hit an enemy because of hastened katana, your target does suffer a movement speed drop because of frost hammer. Frostbound hammer also helps you stay alive a little longer with the health it gives you, but that is not the main purpose of it. Hastened Katana gives you some more attack speed and movement speed, so you'll be able to catch people that you usually wouldn't be able to in addition to getting some more butcher blades true damage off.
To the person who doesn't read abilities in depth, they may have missed that Baka's passive and his eat give him extra movement speed. This, in combination with his leap, makes him very easy to catch up to people with. So, if an enemy is running away from you and you're near a minion wave, have a quick little snack.
Baka's ultimate, regurgitate, has him vomit up all the minions he's eaten and apply a slow in a fairly large area. If you happen to see someone sneaking away from a fight, leap over the front lines, use your ultimate, and go to town by chomping down on some divine flesh. With the frostana combo, you should be able to keep up with them very easily. If you didn't leap to get to them, be sure to watch for enemies around you. You're worth more to your team alive than dead, so if you get in trouble trying to secure a kill, leap out of there as quickly as you can.
Bakasura doesn't have impressive clear. Odysseus' Bow fixes this problem with the jumping lightning every fourth basic attack. In combination with your eating of a minion about every other wave, this should make you pretty good at clearing out minions. Keep in mind that in Arena, the buff camp monsters are the big jungle camp monsters. When they are eaten, you gain 2 minions for your ultimate. I recommend quick or instant casting for the eat because it won't go off if you can't do it. Saving the jungle camps to eat is often times in your best interest, but if other gods are headed towards you (to kill you and/or kill and take the buff) just kill the buff and keep the exp and gold away from them.
If someone is building stacks on your team, I implore you to use the other build. It may have slightly less attack speed, but it will pay off in the long run when that teammate has maxed out stacks and doesn't hate you. Eating only when necessary also helps to alleviate this problem, as only 3 buff camp monsters are needed for you to have all the minions you could possibly have for your ultimate.