Parry

There is a pretty good counter to the dark orb attack. If you get behind him the orbs no longer lock and you get a few seconds of cheeky damage.

For the first boss battle with the pursuer in the Forest of Fallen Giants you can bring Ruined Alfis with you into the battle

Was having trouble with the pursuer in Iron Keep for a few attempts, using same gear as I did for Smelter (Alonne Capt. set, Old Knight Shield, Estoc +7) since I was attempting him right afterwards. Tried switching a few different things around with no improvement until I tried the fight with a Tower Shield +1. A greatshield makes this fight a breeze because of the reduced stamina drain from blocking. Aside from the avoiding the curse stab I didn't even need to roll, I just tanked, spanked and strafed right the whole way through the fight.

you can summon Alfis down in the skeleton room and drag him up to the boss to fight him in ... scholar of the first sin

He's also in things that betwixt (SOFTS)

Who the hell thought putting two of these at once was a balanced fight?

Pursuer stop pursuing you if you're out of his attack range

Adding to the lore theories, he is also wearing a distorted version of the basic knight set.