Armor Team help

Well, first off you should pick Henry for sure.
You'll want a mage on your team, and Henry is just a very solid unit.

Next up, Effie might be a good option. +res and Berkut's lance if you want to go with DC (and are willing to give up a Berkut), But given the team you could also just focus on making her a wall.
I would normally say Brave Hector, but the amouth of merges and Hector's IV really tips the favour for Effie.

Black Knight is the only red option and very solid. Can be strong at budget, and amazing with investment.

The last is up to preference, kinda sucks that the two best tanks are -def. Neutral Hector is probably a good choice, he can take on archers that are too dangerous for Henry.

It helps you if provide some sort of role that you want each unit to accomplish.

Anyway, for Effie, I think that +Atk / -Spd is going to be better so that she can deal more damage, especially if you run her with Wary Fighter. +Res / -Spd isn't bad by any means, but I think that spread is more suited for the Berkut's Lance build (unless you are already running that), while +Atk is going to be more useful for a variety of different builds.

After that, H!Henry is really nice for providing the Armor Boots support, as well as being a fast Mage Armor--something that is pretty rare and locked to seasonal units, if I remember correctly. Those IVs are looking pretty nice, as well; definitely include him in your team.

Black Knight is still an amazing unit, despite being powercrept by Zelgius in almost every way possible. A Distant Counter weapon, a broken Special in Black Luna, and a really solid stat spread of 34 Atk/ 34 Spd / 35 Def are nothing to scoff at. He'd also round out your color coverage.

Finally, I think that either one of the two Hector is really good for filling out that final slot. Both have access to omni-breaker (which consists of Quick Riposte in weapon and seal slots, and Wary Fighter in the B-Slot) to allow them to prevent doubles while also doubling themselves on Enemy Phase. If that isn't your cup of tea, base Hector has access to Berserk Armads via refinery, which turns him into an offensive powerhouse, while B!Hector has innate Bold Fighter, which is pretty broken.

My current Effie is +Atk/-Spd and +10 merged, but I gave her Berkut's Lance+ with Res refine and her defense/resistance is still 37/38 with Berkut's Lance skill in effect. (No, I never came across a +Res/-Spd Effie, but if I ever do, I am thinking of using that one since I like having Berkut's Lance on Effie to fight against dragons and mages well.)

+Res/-Spd does give her her superboon. If you want to keep the +Res Effie and make her a mixed tank, then go right ahead and finish merging her, but having +Atk would push her attack to a monstrous 61 attack (since 14 might appears to be the minimum for the most common played lances), or 55 attack if running a Brave Bow on her.