Starting in the "Undead Parish" there is an armored boar. Is there a better way to defeat him than head on?

Well, depending what you mean by "head on", it is possible to melee the boar and perform back stabs. If you aren't heavily encumbered, it's pretty easy to maneuver behind him and it should only take 2-3 back stabs.

Another option is to throw an alluring skull on the bonfire. He'll damage himself by running into the flames.

Essentially, this game is broken as the manner in which enemies reset if disengaged makes them incredibly vulnerable to attack for a short time. No enemy in the game will chase beyond a certain point, effectively allowing you to deal free damage while taking none. That is "if" you want to break the game. If you want the fight to be somewhat fair and more based on your skill as a player, it may take a little bit of trial and error, but every enemy has weakness.

We know the boar is quite heavily armored, which makes slashing and blunt attacks, more or less, ineffective. So you are left with Piercing type attacks and magic. If you didn't really get any magic the fight will be more dangerous as you are constantly within reach of those tusks. In this instance, backstabbing would be the way to go. The boar does, unlike most other enemies, have an incredibly small backstabbing gap so this may take some practice and a few deaths to get it down.

The only other real option for this fight would be magic. Again, some trial and error with different types of magical attacks would be required to see which is more effective and leaves you vulnerable for the shortest amount of time. I think at this stage you really only have a few magic spells available, including Pyromancy. So at least you wont need to do much trial and error.

Really the only other thing you need to worry about is dodging. If you can't get out of the way or fully block the charge of the boar, you are dead.

If I was to do this fight the fair way I would rush through the archway, past the few hollows near the stairs heading up to the terrace and rush the archers up there.

-Once you kill the two archers, back yourself against the wall on the far end of the archway the archers were on, facing back the way you came and which all of your enemies must now come.

-Take care of the hollows as they come at you, they should only be able to fight you one on one, so easy fights. Parry and riposte for the sword wielders, kick and fast combo attack for the spear wielders.

-As I've never done this fight this way, I don't know if this next part is possible. "IF" the boar is able and does in fact make it's way up to the archway where you have staked yourself out against the hollows, you jump the hell off before he starts charging you. Typically enemies will run back along the path they came to get to you instead of jumping off. This isn't always the case, but it happens the majority of the time.

Once you have taken out all the Hollows, you are really at your leisure to engage the Boar in any way you see fit. Hope this helped, and good luck!