Did you try Bloodhealing before? You can use it on Undead Army, a Revenant, an anyway dying unit, or whatever - it is one of the strongest heal spells of the game.
Winter Witch also can offer great sustain, if you can manage the micro..
LSS green was also slightly buffed, as it can vacuum up revenants, but going that way can be a challenging way to play.
Very important if you want to play pure LS, is that you bring crowd controls like Frenetic or(!) Freezes.
Pure LS decks should be absolutely viable for any content around. But it can be a challenging deck to play with a TON of micro management options.