I'm pretty sure this topic may have been brushed upon, but I figured I'd give my two cents on this Issue.

It's no surprise to any player that Fyro, the Fire Knight is a very challenging Dungeon boss provided you don't have the Champions to take him on. Multi-hit Standard Attacks (A1s), Heal Reduction Debuffs and Counterattack and Reflect Damage buffs do come in handy in wearing down the durability of his shield. However, not every Champion has these abilties. Thankfully, the folks at Plarium have created a Champ that will help out a lot with this: The new Champion that will be obtained on the 150 Day Login Milestone Reward, Lordly Legionary. With his Extra Hits on targets with Heal Reductions, Reflect Damage buffs for his whole team and Speed Down/Turn Meter Drains, he truly is what Plarium calls a "Tough Fire Knight Raider".

Sounds great, except for one small issue: He's a Magic Affinity Champion... 

This is a problem; it would still be a problem if he was either a Force or Spirit Champion. The Fire Knight, like the Spider, Ice Golem and Dragon, changes his Affinity with every new stage. A champion like Legionary will be disadvantaged against Force Affinity Fire Knights. For a Champ to attack an enemy whose Affinity beats there carries with it more problems than suffering Weak Hits. You also suffer a reduced chance to land Critical Hits, plus Debuffs will always fail to be applied on Weak Hits as well... 

Plarium, I know I'm a very small fish in an otherwise big pond here, but going forward, if you plan to design Champions who are specifically designed to combat Dungeon bosses like the Ice Golem, Fire Knight, Spider or Dragon, you should not make them Magic Affinity, nor Force nor Spirit...

Any Champion like this should be Void Affinity 

That way they can truly live up to their role as Specific Dungeon Raider without ever being disadvantaged all the way up to the final stage at Combat Level 280. The Champion won't have the upper hand, but neither will the boss. For example, Fellhound, a Rare Demonspawn Champion, is lauded for taking on the Fire Knight as it attacks with an AoE that can apply Speed Down, and can apply a Reflect Damage buff to his teammates, all while not suffering any disadvantages against the boss due to being a Void Champion. 

Anyway, I just wanted to share my two cents on this matter. Again, I'm sure this has been discussed before, but it wouldn't hurt to bring it up again. I do hope you at Plarium consider changing Legionary's Affinity to Void, or if not, make sure you do this for any future Champs you design who are designed to take on Dungeon Bosses.