Most of the time the heating method is a waste of time. But to even do that method properly, you need to have a surface thermometer or two laying on the neck to keep from damaging the neck, because the amount of heat you will need will be right on the border of causing damage to the neck. Plus, the neck would need to be held in a back-bow while doing it, because you need to over bend a little in the direction you're trying to get the neck to go into, because it's going to still want to spring back to how it had been, so you hope that by over-doing it, it will end up close to where you want it.
*And* usually the heat method is chosen because a neck doesn't have an adjustable truss-rod or is valuable enough that you want to try to avoid removing fret-board wood as much as possible.
You should measure that dip with an SE and gauges. If it's not extreme, it can be leveled out. If you do level the board, maybe try a Martin repair department trick, where you have support under the headstock and about 12 pounds of weight on the body to simulate string tension (I don't know how they came up with 12 pounds, but I just take their word for it, since I never experimented with how much downward weight one would place on a body to simulate string tension)
You probably already did this, but, if you can take the t-rod adjusting nut off, do that, clean threads with a pipe cleaner, and a little thick lube on the threads and the bearing face of the nut. Put the nut back on, but leave it loose. Clamp or pull neck into a generous backbow, hold it there and tighten the t-rod nut as much as possible (yes, a chance you'll bust the rod, just quit when it feels like any more turning and something is going to bust)