Well, the cons of these changes are beginning to show. I'm losing almost every battle in the Arena (even to teams 50k under mine, really pathetic). I guess it's because Kael has now 500 less ATK. My current team is Gorgo (leading), Kael, Ronda and Dhukk. Maybe I should build some champion only for the Arena, Genbo maybe?

Genbo is great for arena. :)

For arena, I recommend Basher. He gives your team basically an extra turn, as the opponents surviving Ronda's first hit can only use their A1 skills. And, the real reason why Basher is so good, this effect (increase cooldown of enemy skills) is not a debuff and will effect enemies under block debuffs and even in Stoneskin armor. Despite the fact it's not a debuff, it still needs accuracy to land.

Farming campaign for faction guardians sounds like a really good strategy. I'll be pulling a load of ancient shards this weekend, but if I'm missing any rare faction guardians for key factions, such as for champions used in clan boss, I'll spend next week farming campaign for those rares to complete them. :)

One more con of the new gear on Kael: one level less in Spider, from 11 to 10. I use Psylar there instead of Gorgorab but anyway, not enough DPS. I had to build Psylar with a lot of DEF, HP in order to survive, and Kael has 500 less ATK. But I can buy the masteries for Psylar, maybe that helps ...

Maybe I should build an specific champion for Spider. I'm considering Hellhound, but I guess that the build for Spider must be different than the campaign farmer one. And I also have Djamarsa, who seems to be very good at spider.

Thoughts? 

Maneater and Armiger are your champs for Spider, they can reduce turnmeter. The best way to prevent the big Spider from healing is: never let her get a turn.

Well, Maneater is on my team. I have Armiger and Souldbond Bowyer (who can also do the job) at 40, but I think that Maneater can handle with this. The problem I think is lack of AoE DPS. I "downgraded" Kael to get more ACC and besides He and Ronda die rather quickly so I'm left with Psylar, Maneater and Dhukk. I'm hardly managing to beat level 11 ... in more than 6 minutes.

Spider is by far the hardest dungeon of the old ones (before Iron Twins and Sand Devil's Necropolis where released). Maybe you don't have the champs to beat higher stages right now.

Nobody is using AoE damage to kill the spiderlings in later stages. Instead, they are a weapon to kill the big spider with hp burn. A good reason to do Tag Arena daily, you can obtain Drexthar from the bazar. In spirit affinity stages, the spiderlings will attack him anyway (he as weak affinity there), at other affinities, he can force them to attack him with his provoke. It's all about keeping the turnmeter of the big Sider down and using healers or other defensive utilities to keep your team alive and watch them burn later on.

Maybe you should run campaign for food and Dragon for basic gear right now and come back to Spider later, when your champs have better gear and you have more variety in your roster.

Don't spread yourself too thin. Focus on one objective at a time.