Just to ask, you are maintaining your data connection while on a call, right? If on Verizon, then when on a call, by default it will drop to 1X and no data (which includes no texts, I believe), unless you have enabled Advanced Calling.
on att. I get the text message while on the call but didn't notice i got them. On my s4 it would beep when i got a text on call. I am looking for something like that but just didn't explain what i was looking for very well.
Glad you posted about this. Same thing here (AT&T)! I keep missing messages because I don't even notice I get them, most of the time. My Nexus 5's vibration was slightly stronger while on a call.
On my phone I use Sound and Notification, Vibration Type ... I set it to Long Lasting and it's more likely to be noticed. You can also set up a custom vibration pattern.