Can you double check your testing, there are some things you stated that shouldn't be true.
1) You mention being able to hit 12 tgts using PC with EF, but can only get 8 tgts using PC w/o EF. PC has a base max of 10 tgts on a tanker, so if you're able to get 12 with EF, you should be able to hit 10 w/o EF.
2) You said it's easier to hit targets using Shadow Maul over Power Crash, yet PC has a 10 ft radius versus SM's 7 ft radius, and both have a 120 degree arc that should not be buffed by Tanker's inherent (the cut-off for increasing arc is supposed to be a base arc of 90 degree, iirc).
Can you provide evidence of either of those things you stated? If either are true, you will have found a bug.