Heat doesn't really "Chop" through stuff very well.
My $0.02 on the matter:
Heat really isn't going to be good for "chopping" things cleanly. It tends to spread too much. It's easy enough to control at lower levels, since the air can dissipate some, but higher temperatures heat up the air too fast. Thus, if you have enough heat to cut something quickly, you have too much heat to "cut" anything with--you tend to destroy things. Also, it's not a great precision weapon in general. If you heat up something quickly, you're probably going to be heating the up a
lot, so either you're taking a while to do damage or you're risking overkill for more than brief exposure.