FYI Speed Plus is an easy (and cheap) way to get four Evade abilities in the Akademeia event
With the right unit (Lighting or Noctis) and the right TMs (20 sided dice), you can essentially become invincible to physical attacks. Ita an obnoxious combo in Arena.
Here is a solo run on Akademeia ELT using Lighting with 4 Speed Plus abilities and I am only defending in the first waves; basically you will be virtually 100% evade all physical attacks (it will however take damage from magic and abilities, so it can't solo the boss).
In this example I also have 20 sided dice, Vampire Cloak, and Ring of Lucii equipped (the Holy counter allows for quick MP recovery).
Here is a Gfycat link for the first wave of ELT (@6X Speed) completely beaten with only defending, and not getting hit once with over a hundred hits.
Edit: even without near 100% evade with TMs, just the 4 Speed Plus abilities is incredibly useful as you can still evade most attacks (for instance for D. Fina that can counter physical attacks).