Summary of findings
This is for 40 games with each deck, though obviously luck plays a huge part, hopefully the large number of games will even it out some.
Deck version 1, same as the one I last posted: Lost 8, won 32, 6 elemental masteries
5bs 5bs 5bs 5bs 5bs 5bs 5bs 5bs 5bs 5bs 5bs 5bu 5bu 5bu 5c1 5c1 5c1 5c1 5c1 5c2 5c2 5c5 5c8 5c8 5c8 5c8 5i4 5i4 5i4 5ia 5ia
Deck version 2, replaced a frog with a pillar, added Freeze: Lost 9, won 31, 11 elemental masteries
5bs 5bs 5bs 5bs 5bs 5bs 5bs 5bs 5bs 5bs 5bs 5bs 5bu 5bu 5c1 5c1 5c1 5c1 5c1 5c2 5c2 5c2 5c5 5c8 5c8 5c8 5i4 5i4 5i4 5i7 5ia 5ia
Deck version 3, with pendulums but same ratio of water to life, took out freeze and added a frog and a scorpion: Lost 7, won 33, 6 elemental masteries
5bs 5bs 5bs 5bs 5bs 5bs 5bs 5bs 5bu 5bu 5bu 5c1 5c1 5c1 5c1 5c1 5c2 5c2 5c2 5c5 5c8 5c8 5c8 5c8 5de 5de 5de 5de 5de 5de 5ia 5ia
Krathos' deck: Lost 9, won 31, 1 elemental mastery
5bs 5bs 5bs 5bs 5bs 5bs 5bs 5bs 5bs 5c1 5c1 5c1 5c1 5c1 5c1 5c2 5c2 5c3 5c3 5c5 5c7 5c7 5c8 5c8 5de 5de 5de 5de 5ia 5ia 5ia 5ia
Analysis:
Druid's staff really, really helps.
Krathos deck, obviously adjusted for PVP, didn't have many huge weaknesses, but in return didn't have an overwhelming advantage over anything either, hence the lack of masteries (though it could be my playing). The feeling I got from playing it was that it was really balanced, and was optimized so that chance played a lesser part in winning. I used Purify a lot early-game for some preventative healing, which really adds up, especially with two or more stacked. An extra heal probably would've yielded a lot more masteries. Adrenaline was great, but expensive to play and didn't really come in when I needed it most.
My decks are more dependent on the poison-type Forest Scorpion and a little less on Forest Spirit than Krathos, and also adds some Horned Frogs so that I can still play against Otyguh, and do some extra cheap damage. The AI tends to leave my frogs alone, since they really aren't much threat and have no abilities to kill. Scorpions are kinda useless in the face of any kind of shield, so it's best to get them out ASAP. In return for lack of CC, I was able to place heavier damage earlier. Though, I think ideally it's still best to have some CC, it depends on your playing style, You can switch out a pillar and a frog for 2 freezes if you want more CC, but it can slow you down some if you draw freezes too early on.
Switching to pendulums slows down the the earlier phase because water quanta is almost useless for early game, since the mark alone can sustain one spirit. They were really frustrating to get used to, since you have to wait for the element to change. If they were staggered, they'd be much more reliable. However, switching to pendulums really minimized bad draws, so it about evened out.
Overall, this is a really cheap deck to grind AI3's with, costing only around 400 electrum with about 75-80% winning rate. But don't use it on T50 because you'll get pummeled. It's really only good for grinding.