Hi,
Using multiple devices , all to handle different tasks, is normal for us but its mainly for special environments or specific customer setups. Though one things forcing our hand in certain setups is that we use ASAs in multilple context mode and therefore we need another device to handle VPNs as at the moment only support for L2L VPN exists in the newest software.
We do have setups where we have 2 failover pairs working together. One for VPN and one for NAT/ACL and it has worked fine so far and it has left the configuration on the VPN device very simple.
I'm not sure if I've understood you correctly but are you going to use 3 different failover pairs for that setup?
- Jouni