Not sure about characters joining, but I'm confident that you can still take DoW. It was actually specified by a designer (Gav maybe) that DoW aren't specifically mentioned in the new book because they aren't all rares anymore - various RoR, and potentially other prospective units, are core, special, etc...
I used to run Pikes in the two previous editions from time to time - they suffer a bit from not being able to fight in ranks to the side anymore, and lack of detachments. Ah, but, you say, I can have de facto detachments by sticking small units to either side. But a) these need to be 10+, and b) cause panic.
I like the idea of Pikes, but they're very expensive and fragile, and it's hard to ensure they survive to get their points back. For the same as a Greatsword, I'm just not convinced...