The gateworm is very easy to obtain on the The Giant, just a case of shooting a couple of items with a PaP'd weapon and collecting the annihilator. If you have a Wallpower gobblegum, you can do this in a couple of minutes and not even have to turn the power on.
I do have the gateworm on all maps except Gorod (not started it yet). Shadow of Evil was a little annoying, there is no achievement for completing the full EE so I think a few members on here will have skipped it (you do get a nice looking calling card for it though). Whether BO3 will be like BO1 (where you needed a member of your party to have done the previous EEs for the Golden Rod and the Focusing Stone) is up for debate. If I recall correctly there was nothing like that implemented for BO2 though?
