Yeah, you obviously can't get all of those things in the same team, or at least not early on when you don't have too many options to choose from, and not a lot of skill books. 

Your main priorities are decrease attack and defense, for which you want to aim for 100 percent uptime on the CB, and then poison to do a lot of damage. For that uptime, the things to consider are not only the chance to apply, but also the length of the debuff and the cooldown of the skill (which can be reduced with skill books, but those can take a long time to farm, especially the epic ones, and you may have higher priorities for the books). 

Indeed, you don't have great decrease attack options yet - keep an eye out for a champion like Coffin Smasher, because his decrease attack is on his A1, the attack that has no cooldown, so far easier to have a near-perfect uptime with him. Bogwalker has it on his A1 too, but with such a low chance to apply - and he is indeed fairly poor in general so seems a waste to spend a lot of books on him and then still only have a 50 percent chance. In the meantime, I'd say Jarang is best since he also offers decrease def on the same skill. 

Coldheart is a very important champion but mostly for endgame. Her signature skill Heartseeker is heavily nerfed on CB so she doesn't offer much there. And on other content, since Heartseeker scales off enemy max HP, it does quite poorly in early and mid level dungeons, it's only in high level dungeons that she puts out massive DPS compared to other champions. The turn meter impact of Heartseeker is great for Fire Knight and Spider at any level, so for those dungeons you can use her much earlier - but then with different gear, focused primarily on keeping her alive and high accuracy, without caring too much yet about her offensive numbers. 

Thank you very much for the through answer, helped quite a bit to understand that attack debuff is not to be undervalued. Ill start off with Apo, Fb, Kael, Bulwark and Nazana as she ranks higher than Jarang and Ill hope that I get something to replace both of them for the attack debuff while leveling Naza for CB and other content later.

Good fedback on coldheart. She ranked high on ayumilove but watching some youtube videos it seemed that she might have been overvalued in certain places, CB and dragon being two of them.

burned4laifraid said:

Thank you very much for the through answer, helped quite a bit to understand that attack debuff is not to be undervalued. Ill start off with Apo, Fb, Kael, Bulwark and Nazana as she ranks higher than Jarang and Ill hope that I get something to replace both of them for the attack debuff while leveling Naza for CB and other content later.

Good fedback on coldheart. She ranked high on ayumilove but watching some youtube videos it seemed that she might have been overvalued in certain places, CB and dragon being two of them.

Yes, because CB and dragon are both immune to turn meter manipulation anyway and in the CB's case, heartseeker is nerfed on top of that. For dragon, she can still be good in the final stages because heartseeker can still do a ton of damage even if it doesn't change the turn meter, but in early-mid stages she's quite poor there.