Hail of Blades

never really felt great for me. It fell off pretty hard, and only gave a slight engage advantage, from my experience. This is probably why I favored Aftershock initially. Use it if you like it. I'm just not a fan.

Aftershock

is another option. When you engage, it's natural for whoever is not stunned to immediately target you, this rune will prevent most of that burst damage, meaning your ADC has more time to follow up. Aftershock also buffs your disengage a lot. If your ADC is about to get caught by a jungle gank, and you need to commit your W on them to save the little guy, Aftershock will ensure most of the time that you can then E shield and back away to turret without dying. That won't happen with HoB. Also, in team fights you're often committed to saving a teammate or front lining (imagine that?). Aftershock will give you more precious time tanking for your team than HoB ever would give you utility wise with an extra empowered Q or E a second earlier.

Press The Attack

is really good on Pantheon. Your W engage already max stacks it, giving you and your ADC Exposed damage (8-12% increased damage for 4 seconds). Needless to say, amplifying damage to a target is really good. Not sure if it's worth taking if your ADC is using it as well. I would default PtA, if you think your ADC isn't going to take it. Keep in mind, it's still good for roaming, since your other lanes almost definitely won't be using it.

What to choose?

I don't consider any to be critical, though I favor PTA. Feel free to experiment and get a feel for which one you like. I just want to bring awareness that there are alternatives to the meta. The goal is that no one just looks up builds and never adapts to the game they are in.

Your first skill is important!

You always want to start Pantheon with W. Catching the opposing lane off guard in a brush is extremely powerful on this champion, and you should always try this if you're not late due to leashing. Also, your W stacks your passive when fully charged. This means when leashing you should W immediately on it which will kill it faster, restack your passive quicker, and will get you to lane ahead of the enemy team, unless they didn't leash.

Rotations

Your empowered W has much more utility than an empowered Q for the sole reason that it gives you 3 passive stacks almost immediately. This means you can consume 2 complete empowered passives during a single engage. This is why you want to engage with W, into 2 auto attacks, then follow up with an empowered Q (tap it unless they are out of range), if you need to disengage, you can consume the 2nd stack for an empowered E, but that's not usually needed unless you're peeling for your ADC.

Poke

Poking with Q is extremely important. You want to get them down so that you can engage and ensure a kill, and, more importantly, to releave lane pressure. It's even more important on Pantheon because every Q will add a passive stack, and that's when he's dangerous. However! only consume your passive stacks when you know you will not be engaging or peeling before you can restack them. You always want to try to engage or peel with an empowered W because it quickly refunds you 3 stacks on hit. This means holding off sometimes on those Q pokes.

Most of the time this is going to be highly dependent on the situation. But maybe I can give you a few pointers of when to and when not to.

Not there silly!

It can be very tempting when you have a global ult to charge right into the middle of the enemy team when your team is looking to engage. This is not a good idea. Pantheon's only built in defense is directional, which means you're built to get picks, not straight up engage everyone.

So then, when?

You want to ult from an angle that will give you a pick on someone that is straggling. This can be by ulting into a brush from the side, or even behind so the poor fellow is sandwitched between you (who will CC him), and your teammate (who will kill him).

Under tower

Ulting under friendly tower can be extremely successful. Quite often when the rival lane has started hitting your tower, they will greed heavily for that plating gold. If you see them overstaying (sometimes they will even be without their support), Ult in. Remember that your Ult can easily clear the wave, which will leave them potentially in turret range when you W stun them. Followed by an empowered Q tap, you might be able to turn that plating greed into a kill. Just remember not to ult right on top of them, but somewhat behind, so they are in range when they fall back. Obviously this is better if your teammate is there as well, but it's doable solo if you are not too far behind.

With the new items out, Panth feels even better than last season. I would highly recommend trying him out if you like the champ.

If you're in Diamond+ he is actually a really good champ. He can dive turrets like Alistar, but have some insane pick potential, and can roam even better. He's insanely good into enchanters, such as Yuumi and Sona (if you get picks early, and don't get outscaled).

Even though I don't recommend him over other supports, you can still play him though. I only softly don't recommend him in low ELO. The thing is he is insanely fun to play, and sometimes that's more important than gaining a 1-10% better win rate. Keeping your sanity and having fun is really important at times. So, feel free to try him, and see how it works out for you.