They're great in EB's, great in out of system wars and can be good in system wars. Currently, with the right combo, they can hit a hansel with zero cash out, but who knows how long that 'feature' will last.
Balanced/hybrids are the best, stock up on pots, allies to plug the gaps pots can't fill and you will be fine.
Hybrid is great. Best of both worlds, but like it was said earlier, you need to stock up on allies. It's worth it though. I like being sneaky with spies but also attacking so it's up to you OP
With enough allies an all stable build can hurt anyone. Hybrids are great in eb, however they are forced to fight with troops pinned in war as a focused build will tear through them. They do have the advantage that as they are such great earners in eb they can accumulate more allies on average, but that takes a long time to kick in. Hybrid builds are for experienced players and strong ally traders.