I not not sure I understand the team correctly. Since:
1.Only the enemy facing pet has exp. No share item nor tech tree.
2. Swap only happen when pet die. And the next pet will be assign to a new fight. No support skill or buff. In other words, no teamwork at all.
Then, why should we have second pet in our team? Instead of spending time on the second pet, we can just farm with the first one and make it stronger.