Hey Will,

I have the internal map for the defroster delay relay. It tells me you should be able to double them up on the trigger side without diode isolation just as you planned. Go for it.

Or perhaps easier, just run the loads in parallel from one delay relay. It will handle them.
--
Art Benstein near Baltimore

... He picked up Milli-Amp and took her for a ride on his Megacycle.
They rode across the Wheatstone Bridge, around the Sine Waves,
and stopped in the Magnetic Field by a flowing current....