Ranged attacks with a Bow are possible. It is best to utilize debris to block their missile attacks.
In Undead Parish, another approach is to lure them to the top of the lower stairs to render their horizontal sweeps useless.
Another effective approach is to hide behind debris that is NOT destroyable, such as the stone ruins in the Undead Parish, and fire crossbow bolts or arrows at the Titanite Demon while his lightning attacks are blocked by the debris.
A somewhat reliable melee approach is to position oneself behind its free arm, where it appears to be missing a leg. Although this position can be hard to maintain due to its jumping attacks, most of its attacks will miss and it is possible to score an easy hit or two. Its tail can inflict minor damage, as it swings its weapon.
Alternatively, forcing oneself under the left armpit area will cause most of its attacks to swing harmlessly overhead. Staying in this spot, but not behind the left arm, will also reduce triggering the frequency of its jumping attacks.
The Titanite Demon in Lost Izalith is considerably stronger than other Titanite Demons. It is also the only Titanite Demon that respawns, thus, Lost Izalith is the only place possible to farm Demon Titanites.