How far apart are the hoses? Also, you have to dig your hand into the mix to see if the water is fanning out as it goes down, or if it is mostly dropping straight down.

It is entirely normal for the surface to remain dry except for an inch or so on either side of the hose.

What your mix is comprised of makes a difference as well. If you are using Mel's mix you may need to up the percentage of compost to get the moisture to wick into the drier areas well. The peat, once dry, won't wick the moisture to itself. It has to be at least damp before it will do any wicking.

Using a light mulch also helps as the water will kind of circulate a bit from evaporation under the mulch and provide a more even moisture level.

In any case I don't think you will get away with anything over 12" spacing with those soaker hoses (I have the same soakers). Anything over 6" spacing between the hoses and unless you use a moisture trapping mulch you won't get the entire surface moist, but the water should fan out enough as it drops that 3" down everything is watered. If this isn't the case either move the soakers closer together or increase the amount of compost in the mix.