Hello: There is a water flow problem, so that needs looking into. Dip tubes don’t exist in the hot side of normal water heaters. They do exist sometimes in solar tanks and certainly in tanks with bottom connected plumbing. A short dip tube in the hot side of a standard heater would do a few things. It would trap a bubble of air at the top of the tank. It would reduce the available volume of hot water and it would leave the hottest water unused at the top of the tank.
Hot water floats on cold water and that’s why you want to take hot water from the very top of the tank. I’ve looked into thousands of heaters and the thing you’re looking for really doesn’t exist and wouldn’t be helpful if it did. Now, there is a flow restriction someplace and we should find it… 😉