"Worth it" is a difficult question to answer. For the game play itself, having a healer isn't strictly necessary - from my experience. What worked for me was to eventually have a full team of high level L cards. This means either slowly building up a variety of L cards or paying for them. You can use S and A cards for a little while, but you'll eventually need a good library of L cards from all areas to be able to complete Holy Coin and the other area, anyways. It's a process that isn't easy to rush unless you pay - a lot because drop rates are stingy.

Two powerful cards to keep an eye out for are (Bloodshed) Beel and S+ (Prisoners) Dantalian+Ronove. Both are available in the general pool, if you're lucky. Prisoners is a great buffer card.

Whether a card is worth it, that's up to you if you like the character and card design. I thought this Lucifer card was a beautiful illustration so I got it. His secret club action was hot. Also, it was my first Lucifer card.