To my understanding, any Dual-Channel configuration with integral monitoring, or using input-connected test pulses is rated as a Category 4 safety circuit, according to the Banner SC26 Instruction Manual (p.83) :
Each Input in a dual-channel should ideally have its own test pulse. Connecting both inputs onto the same test pulse could result in "false positives" in case of a short-circuit between T0 and T1. Ideally (but not necessarily, depending on severity of application) it would look like this :
You mentionned you use a Banner SC26, but I'm guessing your drawing isn't directly representative of the device? To my knowledge they don't use T# nomenclature for test pulses. They use configurable IOs instead, and have 2 dual-channel safety outputs SO1 & SO2. Your drawing looks more reminiscent of a Pilz SC.