QUOTE(panda272 @ Jan 27 2021, 02:45)

I've recently hit a sharp difficulty increase playing with 1H/light
At level 150 monsters gain their own spirit bars, so you'll be receiving stronger attacks, especially if you play on the strongest PFUDOR difficulty.
1H/light isn't the best style to play, as 1H relies heavily on getting hit to counter-attack and stun monsters after a successful block with your shield, yielding you a nice amount of overcharge so you can keep your spirit stance constantly on.
The evasion from light armor gets in the way of your blocking, as the evasion roll comes before the one for the block chance, so you'll end up doing less blocking and less counters.
A stunned monster can't attack you, so you don't have to worry about evading or blocking it.
As you are very close to level 200 by now, it's a good time to pick up some heavy armor, no matter if it's just plate or the better power version, and try it out to see if you can survive better.
QUOTE(panda272 @ Jan 27 2021, 02:45)

1) When should I be considering soulfusing equipment and using the item world
You get a very limited amount of soul fragments per day, so it's best to only soulfuse Magnificent+ equipment that you are unlikely to switch any time soon.
An example would be a Magnificent Ethereal Rapier of Slaughter, which is the best weapon with adequate Prefix and Suffix for a 1H build, and you'll be unlikely to find any upgrade for it unless it's a Legendary Ethereal Rapier of Slaughter.
As for armor, you should either aim for plate of protection/warding in case you still have trouble surviving, otherwise power of protection/warding can be an upgrade, with power of slaughter being the best for faster clearing speeds once you have no issues surviving monster attacks.
For the Item world, you should definitely get at the very least your weapon to IW10, as it will switch it's physical/elemental damage to void, which monsters don't have any resistance to, and you'll be constantly dealing more damage that way.
Item worlding your armor to get the Juggernaut potency, granting an extra 2% max health per level, is also a good idea, but due to having 7 other available potencies that can appear on armor, it might be a harsh investment of Amnesia Shards and/or credits if you use an Item World service, so it's up to you if you really want/need more max health or not.
QUOTE(panda272 @ Jan 27 2021, 02:45)

2) Is it normal to be chugging mana draughts and potions basically off cooldown and using cure fairly often
Draughts are extremely cheap to purchase from player shops in HV Persistent, so you can easily get a big stock of them for cheap, or even for free, and use them on cooldown with no worries.
QUOTE(panda272 @ Jan 27 2021, 02:45)

3) Which supportive spells should I be keeping up at all times
Spark of Life is a must to avoid unlocky deaths to multiple monster SP attacks in a single turn.
Protection has a long duration once cast, so there's no reason why not use it, as it has a very low MP cost for the extra defence it gives you.
Regeneration is a great heal over time spell, and very useful instead of leaving all your healing to cures and health potions, even if the health you recover per turn isn't as great as a single cure.
Absorption can be useful, but it can only absorb a single monster attack, and you'll have to recast it every time if triggers, so I don't particularly find it very useful at my level, but you should still try it out.
Heartseeker is a pure increase to your damage, as well as giving some extra crit chance, so even though it consumes a lot of MP, it's worth using, especially if you get the chanelling buff, which lets you cast any spell for just 1MP.
Haste and Shadow Veil can be useful if you are having issues surviving, but as Uncle said, later on when your health isn't even bulging you can drop them to aim for faster clear times.
At level 200, you'll get access to spirit shield, so you should definitely use that one as well, but keep in mind that it will consume some of your SP every time it protects you, and can leave you in though spots if you forget to bring spirit potions to battle, so always keep a healthy stock of them on you at all times.
TD;DR: use all supportive spells available to you in case you are having trouble surviving.
If you aren't having trouble surving in higher difficulties, and don't need to use cure every few turns, then you can try dropping haste and shadow veil for faster clear times with your 1H build.