I've beaten Demon Souls twice now, once with a Royalty build and once with a melee build.
Magic definitely makes the game easier at times, but you will still need to level up your endurance and vitality a decent amount because there will be times that you have to get stuck in. Some special enemies are very magic and fire resistant, so you have no choice but to get stuck in (or poison them).
Also NG+ is brutal for melee builds in this game. My melee character gets one shot despite having high vitality and the best armour by an alarming number of enemies. NG+ increases the health of all enemies by at least double, and their damage by up to 4x. Yikes.
I think the main things to remember for whenever you try it Mas are:
1. Keep your equipment weight at 50% or lower - this will allow you to fast roll, which makes dodging a lot easier. If you find you are taking too much damage, make sure your equipment has the right resistance (fire, magic, etc) for the region you are in, and invest in vitality.
2. If you're stuck on one of the worlds, that's a sign you should go to a different world. You'll often find armour or weapons in one world that's designed to help you out elsewhere. Pay attention to the hints other players leave around the world though, some areas are best approached with blunt weapons, others with piercing ones.
3. Kill yourself in the Nexus.
4. Rings are really useful. Everything stacks in this game, so find a ring that regens mana or hp and it will stack with armour that does the same. The Thief Ring is also super handy. It makes it harder for enemies to detect you, which is so useful in certain stages. It also makes getting backstabs easier as you can catch enemies by surprise.
5. If you do go Royalty, you'll find a really good weapon in the first area of the skeleton world if you're brave enough.
6. If your damage sucks, you might be overdue an upgrade to your weapon. The blacksmith in the Nexus is fine early on, but you'll need to find the better smithy to get the good stuff.
7. Make sure you have enough stats to use the weapon/shield you've equipped. If you don't their effectiveness is nearly useless. That said, you'll still get passive bonuses (e.g. regen) from having them equipped. I played a lot of the game with a shield slung over my back and two-handed my weapon just for the regen the shield gave me.
8. Don't consume the souls you get from slaying bosses! These souls are more useful for learning powerful spells or getting unique weapons from later on.
9. Make sure you've got enough grass. You have to buy or loot healing items in this game and it sucks to run out of it, die to a boss, and know that you have to grind for it.
10. The harder an area is, the easier its boss tends to be. Many bosses have weaknesses that can be exploited to make the fight easier. If an area or boss is too hard, you can always summon a friend to help you out by setting a password via your network settings.
Now you know everything you need to so you better get streaming one day