Raspberries too wet in muffin
Raspberries are going to leak a little and stain the batter of any muffin they are put into.  Muffins with whole berries are going to have reduced shelf life due to this.

Frozen raspberries would be even more leaky, as the freezing and thawing will soften them.

To make a raspberry muffin, you have to accept that raspberry is very moist, so you cannot overload the muffin; the have to be used with a moderate amount of restraint.  

Dusting the raspberries with flour (from the main quantity of flour in the recipe) before mixing them into the batter may help form a barrier, although I wouldn't count on a dramatic change in outcome.  I have not personally tried this, though.

If you don't mind a completely reddish muffin, you can puree some or all of the berries, and use them as a substitute for some or all of the water or milk in the recipe, as they are about 87% water to start with.  This will allow you to balance the liquid level.