What you describe is actually two separate problems, but both a result of improper die adjustment and/or inattention.
First, assymetrical sizing. This can be caused by two things. First, a mis-aligned press. If this were the situation it would consistently occur with every case sized, so it can be eliminated. Second, a case not fully seated in the shellholder. If you don't get the case fully into the shellholder there is enough friction on the head to hold the case out of line with the die which causes the case to enter at a slight angle. Sometimes you will hear a distinct "snap" as you complete the sizing stroke. Pay closer attention and be sure the case is fully seated in the shellholder.
Second, the "ring" that forms just ahead of the case rim by 1/8" or slightly more. Depending on dimensions of your die and brass the degree will vary. The cause of this is that the solid portion of the case head is larger in diameter than the die ring. You are trying to size the solid portion of the case! You are over-working the brass in the web, and putting far too much strain on the carbide ring, which can break the insert Maybe this is why you thing sizing these cases takes so much effort! Instead of lubing the cases, be sure the press ram is clean and lubed. This reduces effort for all operations. There is no reason to use lube with a carbide die with straight cases.
What to do? There are several approaches. First, back the die out a turn or so, you only have to size the portion of the case which expands on firing. The solid head does not.
Second, neck size only. May or not work if you are shooting only one gun in the caliber.
Third. Spring for the Redding double sizer die. This will size the neck adequately to hold the bullet while sizing the remainder of the body only to SAAMI Maximum case diameter, instead of under minimum as the standard carbide sizer does.
Fourth. Buy a Lee "Carbide Factory Crimp" die. This can be used two ways. First, if you are shooting "standard for caliber" diameter bullets (.451 for .460), neck size only as much as needed, seat and crimp in two steps using the Lee CFC die to crimp and post-size the case body. Second, size in two steps. Neck size with the standard sizer, then, in a separate operation, size the remainder of the case body using the Lee CFC die. You have done exactly the same thing the Redding double ring die does, but without paying $100+ for the one die!
Either of the last two methods will reduce the amount of working the brass is subject to, and should result in somewhat longer case life.
Yes, sizing in two operations takes a bit more time. Loading for one of the big S&Ws should be more about consistency and care than simply "getting it done as fast as possible". Slow down, take more time and care, learn to enjoy reloading for its' own sake, instead of just loading to shoot more.
For Dang1182,
You don't need to buy another sizer die. The .45 Colt/.454 die is correct. It won't cure any problems, just waste money. The only real difference among the three cartridges is case length, diameter is identical. As a practical matter a .45 ACP die would work too. Keep what you have, read what I have said above and take it to heart.