During the last few days I found a never used synergy for SoP. Have you ever used them on scorpions ? [...]
Shards are 'Other' cards, and they have a reason to be such. All of these cards are somewhat universal, and could take a spot in almost any kind of deck, but many of them are considerably stronger when used with certain elements. Like all the other shards with their respective element, SoP also has an increased efficiency (at least in theory..) when played along with Water creatures, but its main purpose would be the attack increase, yes.
Sadly, you're still better off using Momentum/Blessing/Chaos Power for instatly applying their poison, as the 1 turn delay lets your opponent get rid of/ignore them easily (provided there's some CC or shields at hand). Also, unlike other buff cards, SoP does not provide additional HP for anything non-Water - rendering them totally helpless against such countermeasures.