Tank Team?? Yay or Nay?

Running a full-tank team severely inhibits movement and makes the team into a lunch platter for mages like Nino, Sanaki, and Linde. However, they are unrivaled against everything but Armorslayers and will destroy any infantry teams.

I actually run a semi-tank team myself for Arena defense, and I've gotten quite a few wins in Tier 11. Here is my team.

5* Rebecca (+Spd -Def) with Silver Bow+, Ardent Sacrifice, Luna, WB3, and Seal Atk 3. This setup is my ranged nuker and mage killer, who can either kill or severely inhibit the abilities of threats to the team.

5* Effie (+Spd -HP lol) with Silver Lance+, Swap, Noontime, DB3, and WF3. She functions as the counter to red lords and can maintain self-sustainability through her Noontime charge time being not that long. Combined with Wary Fighter, any combat with a Brave weapon user automatically charges her special. Swap gives mobility and utility.

5* Hector (+HP -Res) with Armads, Swap, Pavise, DC, Seal Def 3, and Goad Armor. Not only does he buff Effie, but he also is a solid answer to a Heavy Lance user as well as most blue mages provided that Rebecca debuffed them first. Swap gives mobility and utility.

5* Lyn (+Atk -HP) with Sol Katti, Galeforce, Defiant Atk 3, Escape Route 3, and Spur Spd 3. Lyn can potentially take out half of a map with her skills, teleporting around and dueling any Hammer threats as well as Nino and Sanaki. She also serves as a reliable meat shield for Hector and Effie in order to trigger her skills as well as protect them from harm.

Honestly, if you were to go with Hector, Zephiel, Ninian, and Reinhardt it could be a decent defense team. Hector is Hector, Zephiel threatens mages by making sure they HAVE to snipe him through untraversable terrain and they can't just run up to his face and do it (damn that Wary Fighter), and Reinhardt+Dancer is threatening due to their effective range. You'll really have to make sure the armored units are carrying either Swap or Pivot to have any kind of mobility though.

In all honesty, making a team that's defensively sound is way harder than making a team you can get wins with in arena. Piloting a team against bots is generally really easy (save for a few hard to bait units) and you could feasibly just take your current team, swap out a slot for a 4 Star bonus hero, and do fine. That is, assuming you're not running something like Flier Emblem where all your units need to work together to that degree.