Gold Scorps are amazing! But only after you have the t11 research full, before that they suck because they have very low damage migration.
For timers they are to slow, but since the new temple change they double benefit from the runes. They benefit as normals units from attack/health buff, and from the heal buff - also their selfheal is based on their health. The selfheal heals more then a strong Vega.
Gold Scorps are very strong in duells and the only valiable frontline to do serious plunder runs (except bronze runs) as Lich (with 4 loaned rockets and good heros).
Skelettons are also strong with high research, but the perma dead mechanic makes them to expensiv in my eyes.
Spiders are strong an mainstream. For duells you have some options, you can run Spiders and frontline (swords, monks, scorps) or you can focus on Scorps and let the heros do the dmg (with 2-3 spiders). Since i got my lvl 13 Scorps (Castle 37/38?) i was able to win much duells (against lvl 40 player with double power then me) with only bronze scorps because i can outstat much players, and have an strong Jacques and Rose.