The Matchups - what can we take head on?

I agree that mournfangs are a unit that is designed to obliterate Str3 T3 enemies.
etc

I agree with your entire statement 

The threat in different charge ranges and the swiftstride are the good points. . Maneaters can get the swiftstride, but don't increase the threat range unless they couple it with scout or vanguard.

When you look at how a unit works, it's sensible to look at the thing as a whole.
Yes a unit is the sum of it's parts, but all those parts together to make one glorious whole.
Maneaters can get the threat range in the way of Swiftstride, but don't have the high movement too which gives the higher threat range.
Couple that with a great AS and all the above average S attacks, you get that glorious whole.

I really need to get mine built...

I have 4 spare most weeks if you wanna borrow?

tempting