Tyrunt took some babying, I agree, but his Bite is powerful, and he gets a nice set of TMs. The only problem is lack of Rock and Dragon STAB for a while, and his lower defense. I could see either A or B tier, but I edge towards A. Tyrunt is still quite useful before evolving and after evolving Tyrantrum is incredible. Earthquake, Crunch, and Dragon Claw are the only three moves you need to OHKO or 2HKO most things, so you can throw an HM on him to help your in-game run. He's a great pokemon. He evolves at level 39, not 40, by the way.
Name: Litleo - B or C Tier
Availability: Route 22, before the first gym. This is one of the earliest pokemon you can get.
Stats: Litleo is primarily a speedy mixed attacker, though it prefers special. Base 72 speed & base 73 special attack is pretty good so early in the game. When it evolves, Pyroar has 106 speed & 109 special attack, though it's defenses are average (~70). One problem is it's possible ability, Rivalry. When facing an opposite-gendered pokemon, attacking stats are lowered by 25%. When facing a same-gendered pokemon, Pyroar gets a nice boost but this is a very unreliable ability overall, so hope you get an Unnerve Litleo.
Typing: Normal typing is both a blessing and a curse. Obviously normal STAB, especially so early on, is fantastic, but there are a ton of fighting typed pokemon. Litleo/Pyroar won't take SE hits from fighting types well. Fire typing is excellent, as there are not a whole lot of water/rock types in Kalos.
Movepool: Decent movepool. Litleo starts with STAB Ember (at level 5), Work Up at 8, and STAB Headbutt at 11, which is wonderful. However, you don't get a boost until Flamethrower at level 36 (at which point Litleo evolves). Being a special attacker, there are not many useful early TMs for Litleo. Pyroar gets Hyper Voice at 48, but until then you're stuck with Echoed Voice for normal STAB. So basically: excellent early game, mediocre to bad mid game, then good late game once you get Hyper Voice.
Major Battles: Does really well against the first gym, doesn't solo it though due to Vivillion's defenses. Has a rough time at the next two gyms, then dominates Ramos. Gyms 5-7 are all okay for Pyroar, nothing great but it's not a bad match-up. Pyroar sweeps Wulfric (except for Cryogonal). Pyroar beats one of the E4, loses to two, neutral to the fourth, and does fine versus the Champion & your rival. You need a balanced team, you can't solo with Pyroar.
Additional Comments: Good speed & special attack, good early game STABS, late game but powerful STABs, and lowish TM usability makes Pyroar/Litleo a decidedly average pokemon. Super-early availibility makes me lean towards "B".