Why do you want the divots straight? They should be going slightly right - which indicates a slight "from the inside" swing. The ideal swing path is inside-square-inside. Impact should be towards the end of the first "inside" and the beginning part of the square.
I watched the PGA tour players while I was in America and on the long
irons and medium
irons, they all have divots pointing slightly right and many of them. Geez, those guys do serious excavations!
They are awesome to watch. A few of them let me tape their swings too!
But if you want a squre swing path, the best drill I know of is the "tee drill" and works like this:
Place a tee or other visual aid (sometimes we use plastic discs) in line with the ball but a foot or so behind it. Put another one a foot or so ahead of it. Now swing away and focus on the 2 visual aids. Make certain your club travels over the "behind" visual aid on the way back and the way down and then over the "forward" visual on the through swing.
I like to explain drills with 'feelings' so you know whether it is working correctly or not and it also gives you a sense of the motion required in the swing execution. It will feel like the club goes back and comes into impact much straighter and then thru straight at the target. A little like a stiff-wristed chip shot.
If you don't get the feeling, stop. Now take short, stiff-wristed chip swings using the visual aids. Once you've done that a few times and hit a few golf balls, extend the swing to your right hip and swing thru to the left hip. When you've got that, swing a bit longer and then a bit longer ... until you've got a full swing going.
Ok? Glad to hear your ball flight is corrected. (
sigh of relief!).