Monsters reset if you go out of their prededined follow range, some of which have quite low range, so yeh they will reset after a long knockback. You need to position against a wall or some scenery like Spunny mentioned, or start running forwards as you do the knockback.

Not really sure what this render distance is, but you can zoom out? It doesn't actually do anything about aggro range though.

If you are using many knockback skills at once, try to position your target against a wall so it doesn't go too far. Or alternate them with non-kb skills.