someone with alt diving in on you isn't really a huge threat, more of a mild annoyance. because of their speed, they are not going to be able to follow you in even a basic maneuver.
What I do.
I try to get them as close as possible, and try to get them to try and force a shot, thus blowing their E. I usually won't make a move until they are 1k back ish or less (depends on just HOW fast they are), and I favor the low yoyo. Split S's cost 2 much E, whereas the yoyo is a happy medium, and the flat turn gets you nothing.
After they miss, I tend to then egress in an opposite direction. Let 'em reverse, blow more e coming after me.
Generally, after 3-4 passes like this, they are pretty committed to the fight, and after they make the BOOM on you, will typically do something dumb. At this point, you usually hold the advantage. They are trying to turn with you, loop on you, whatever, and bleeding their E down so they CAN turn with you. You have the advantage of turning (not saying flat turn, can also be in the vert, yoyo whatever) and it's pretty easy to force a fight on them/cause 'em to over shoot, out turn them etc, etc... The ones that are worrysome, are the guys that make a pass or two, THEN chop throttle, reverse rudder, and bring the fight to you (Levi. for a good example. that guy did that to me in his tempest a time or two. One two passes, then BAM can't shake 'em, he's suddenly slow on my 6) Many pilot do this (heck, I do alot).
In general, I don't consider high alt guys much of a threat, unless there are two or three of them all doing b/z's on me at the same time. THAT get's a bit difficult to time.
(edit) the key is being patient. they WILL make a dumb move trying to get guns on you. You MIGHT only get one quick snapshot, so make it count.