Why would a candle require a much larger wick than normal for its size?
The problem could be the composition of the wax.  Could there possibly be a certain percent of soy wax in the pillars, in addition to the beeswax?  The Wick Guide that you referenced states:


  Higher viscous waxes such as single pour paraffin wax, soy (vegetable) wax, and beeswax, may require (wicks) up to several sizes larger than the recommendations below.


Here is another source that discusses how soy wax can cause problems such as tunneling:


  Tunneling occurs when the wick used is too small and flame does not sufficiently melt the whole surface of the candle. This will result in the candle burning unevenly, a smaller flame, lower scent throw and the candle extinguishing itself.  The best candle tunneling fix is to use a larger wick size...