I have to go with Hazzor on this one. While it IS possible to get jacked by the RNG and Lycanite's (for example, the very first time I made a 1.1.1 test world, I had some nasty world-gen lag on going through the gate and was at half-health before I could do ANYTHING! I died...), it's also possible to survive fairly well so long as you hit the ground running and focus on finding defensible positions (A defensible position against phantoms is one where there is too little room for them to come out of the walls and use their long-range fear projectile attack on you...But you can melee any part of them that starts coming through the wall and knock them back out. It's easy to beat up a phantom if all you ever see are its skirts!). Geonachs? Keep backing and pound the hell out of them. Lobbers? Hold the high ground so lava drains AWAY from you and you do more damage. Against some mobs you MUST commit to full offense. If you charge in and then panic at 1/3 health, you will not survive running away again, but if you just beat them down you'll survive.
In my latest let's play, I was unable to set my spawnpoint when I first came through, and I got swacked before I remembered to try it again. This resulted in me making a 10 minute run through the dark after fighting off multiple mobs at once with my QUESTBOOK because I didn't realize I had my soulbound items (I thought I was just punching). I had nothing but soulbound pickaxe, soulbound questbook, and a couple of stone picks which I made in the dark using wood acquired via Dark Power. I could barely see anything (it is MUCH clearer and easier to see on the let's play, let's hear it for high-contrast video post-processing!) and I couldn't find any coal to make torches (I only had enough dark power for a few wood...I wasn't going to make a furnace and burn 2 wood to get 4 torches!).
So that's kind of "worst case scenario" and it is entirely doable if you think fast, don't panic (much, you're allowed to momentarily freak at geonachs), and play to the resources you have at the moment (nothing but a pick? make a damn tunnel. That way you can only be attacked from 2 directions (barring phantoms) and even phantoms that try to come at you through the walls are in melee range immediately!).
So far the current difficulty seems to reward quick thinking and having a plan. So have a plan. Have a plan for making shelter. Have a plan for what to do when you've been killed and you're stuck making the Worst Possible Retrieval Run. Everything is easier when you have a plan.
Those are things that we all do almost without thinking in Vanilla. Mods make it a bit more complex, but still...If you've got a plan and you immediately start acting on it, you should have a lot less trouble. When you die, figure out why! 9 times out of 10, when your first impulse is to say 'Well that mob is just unfair/OP!', with a little reasoning, you can figure out some way to change the terrain or change your situation so you have the upper hand.
Sometime today I'll be uploading my LP with my finished "8th day shelter."