While this Ajani's -3 helps decks trying to go wide, providing each of your creatures with +2/+2, its ultimate -9 ability provides further payoff for the lifegain of its +2, putting a number of +1/+1 counters on a creature equal to your life total
That being said, for only a two cost card with eight will power, its looking very tempting for ramp decks that dont really need the early game gains as much as they need to ramp up their Inkwell to achieve later game win conditions
You can also abuse infinite combos, which makes The Gitrog Monster a viable combo deck in cEDH
Instead, look for build-around cards like Dread Presence, Empyrean Eagle, Gnarlback Rhino, or cards with traits you know you'll use like removal and cheap ramp (examples: Chandra's Outrage, or Leafkin Druid)
His other ability "Pounce" also means that Simba gains the "Evasive" trait, so he can also challenge characters with Evasive