Well, I've worked in lots of different industries requiring some various rods and processes. I have run some of the 11018 in the past on various things.
I've never really had to work with any tool steels like what your describing. About the hardest I've ever had to weld is some type of AR plate, something really, really hard above AR700, it had its own trade name and can't remember right now, but it was super hard and would crack within 20 seconds of finishing welding it if post heat wasn't applied and either wrapped in a fiberglass blanket or put in an oven and slowly cooled. Obviously pre-heating was required on it.
Inconel is an odd rod to weld as well. Its been a few years since welding with it, but its def. an odd one (and expensive)