im wondering how you deal with Lichs in the tombs
I never had a problem with them, TBH. I don't use poisons or archery-fortify potions unless I'm fighting a dragon or dragon priest, and I didn't bother with any enchanting until very late in the game (like well after I hit 100 archery) (I did have a lot of good fortify-archery gear, but that was all stuff that I found or bought from merchants).
The key is smithing (find and buy a whole lot of good smithing gear, and make a few smithing potions) and stealth. Consistently getting that 3x sneak-attack bonus is critical, and with really high stealth (the silence perk is quite nice), it's incredibly easy to remain hidden, even in the dungeons (with max stealth, I've had enemies walk in front of me without immediately detecting me). There were many dungeons that I was able to clear without the detection eye ever fully opening (at least, until the boss).
The drauger are especially easy to kill as an archer because most of them are sleeping and won't wake until you get close (or you attack them). And it's fairly easy to tell which ones are inert and which ones will wake up (if armored and/or armed, shoot it), so I can pick them off one by one from a distance with all sneak attack bonuses. It's like shooting fish in a barrel. And once I got the Aura Whisper shout (with the silent casting perk), things became so easy that it's started being not so fun (I had to ratchet up the difficulty level the farther I got into the game and ended up at Legendary wishing that there's an even higher level because sneak-archery is just that overpowered.)
(Though not nearly as overpowered as a sneak-dagger build with high illusion magic for invisibility spamming--sneak right up to the a dragon priest boss that's searching for you, one hit kill on Legendary.)
(Oh, and all followers--even Serana--suck if you want to be stealthy. If I bring one along as a pack mule, I'll tell them to hang back a room or two while I go forth and assassinate everything solo.)
Sorry for going totally off-topic. I do very much enjoy sneak-archery (best part of the Tomb Raider reboot), so I might consider this game...