it is 7ft med action xfast would this work well for rattletraps and big crankbaits ? say1/4 to 1/2 weight lures ?

I think you'll hate an Xfast for cranking, especially big crankbaits.  

However, you might like that rod for:

senkos

Ikas

flukes

weightless plastic

drop shot

split shot

finesse jig

shakey heads

sm-med t-rigs

and if it's really as heavy as the ratings (which I don't think it is but could be wrong) any of the above plus a few other things.

You need a reason?

"Because."

That is reason enough to add to your rod collection.  ;D   ;D   ;D

may just buy the cranking specific then it is a tas845cb rod i have a topwater rod i use for topwaters and small cranks but would like a rod specifically for the traps and bigger cranks 3/8 to1/2 im not a 20 rods guy but will end up with about 6 baitcasting rigs all rods will be in the team allstar freshwater seriesd as i just love what you get for the money ! and i kinda neede them to be somewhat versatile ...the 845mc is a mag asting rod so i figured it was kind of a good multipurpose rod ?

I think you'll hate an Xfast for cranking, especially big crankbaits.

However, you might like that rod for:

senkos

Ikas

flukes

weightless plastic

drop shot

split shot

finesse jig

shakey heads

sm-med t-rigs

and if it's really as heavy as the ratings (which I don't think it is but could be wrong) any of the above plus a few other things.

I have an 845 and your list pretty much covers everything the rod works great at.  Very versatile rod.