If ur afraid of your friends/family seeing what you play just set your profile to private (and tell them you started playing rust or idk) and set your status on the chat to offline.
Assuming you can at least access the internet long enough to get the game, you can set steam to run in offline mode, and keep your games playable offline after that.
I'm pretty sure a lot of steam games can be played without internet connection if not all. You can switch to a completely offline mode after you logged in at least once. Ofc things are different if you have a pc that has faulty ethernet port, but that can be solved easily with a phone and an usb cable.
Managed to beat the last boss on my 2nd try on hard mode. An improved "The Mistress" card is definitely a must. Saved my ass every time I face up one of those big ones on the third floor.
My sole DPS was from my 2 Blizzard spells, Chill, bleed spells (Injury and Biting Wind) and sometimes Magic Missiles if don't use all my mana for Blizzard.
Blizzard was extremely OP dishing out more damage than Black Hole at the cost of all your mana. If you manage to get Lucky Dice, Accelerator, Pure Water and Pocket Watch artifacts, the +1 Mana skill in the Survivor tree, and +mana spells like Mana Stream, Blizzard can go dish out so much damage to ALL enemies. Blizzard deals N x 8 damage where N is your mana. With enough mana plus all your buff spells, you can get to 70/80 damage on a good hand. Unlike Black Hole which is only usable once per battle and is only single-targeted, Blizzard is SO much better. Its also affected by your buff spells like Hatred and Amplify.
For survivability, debuff spells were more important than good Shield spells. Great Wall is a nice 2 mana spell that grants 20+ shields, but Defensive Posture is a 1 mana extinct spell that grants you +3 Shields to all shield spells for the entire battle. So your weak 0 cost shield spells suddenly grant 6 shields. But thats hardly enough for enemies that deal 20+ damage in almost every round, not to mention the RNG of you not getting shield spells on your next turn.
Debuff spells like Time Delation were useful in a pinch, but falloff its use in the late game. The really good debuff spells are your Impotence, which reduces power of all enemies by 3 (permanently - which helps for enemies who can permanently buff themselves), Sex Appeal which applies 1/2 Weaken to all enemies, and Chill which deals some damage as well as weakening them. Weaken only reduces damage dealt by 25% though, so don't rely on it unless you also manage to get the Earing of Charm artifact which raises it to 50%.
All in all, I had a blast playing the game. I haven't reached the new level cap yet but I'll work through it as I try to get the rest of the gallery on the third floor. Note: I don't think you get more exp on Hard mode. Got the same roughly 2100+ exp on beating the boss on both normal and hard.