You are correct. The blowpipes have to be skirmishers. However, fantasy does not have the strict WYSIWYG rule that 40k has. I have some of mine modeled so that they could be either javelins or blowpipes (I glued a shield and a javelin to the back of a skink like a supply pack). As far as preference goes, I like the javelin skinks better in 8th edition. Javelins are quick to fire, that means they can always stand and shoot and get no modifier to hit (except for greater than half distance). With blowpipes, if you are greater than half distance and double tapping, you will be hitting on 7s (no poison). If you have no skinks in your army I would suggest that you get 2 boxes of skinks (at least) and model 50/50. Personally, I own about 110 skinks or so. I like hordes of skinks (with Kroxigors).