Is Jalter Lancer worth it?

Jalcer is a very good welfare, but if you are in need of another lancer right now, you can level up proto Cu

Proto Cu is a little more attack heavy than FSN Cu, but he isn't as survivable as FSN Cu is

They are in different Role, my friend.

Jalter Lily is almost same as Santa Raber (also same for Christmas event). They can provide support to the team (although limited). They have strong AOE NP (due to NP5+3rd skill combo). However, generally their NP charge is not top class (NP gain for Jalter Lily is great, but only 1 Art card) hence they cannot frequently shot strong NP. Which means farming is the best place for them. And no strong debuff to enemy and defensive buff means she is vulnerable against any Critical and NP attack.

Cu Pro is top 3 star in combination of Critical damaging+Tanky. Due to stronk ST NP and very good Star Absorption-Critical combo (also short for 5 turn cool-down when maxed, great), he will be Archer/Berserker boss-killer if you dont have SSR lancers, Li Shuwen and Lartoria Alter. Also how can I describe the importance of 2nd skill?

Is it necessary for saving EXP card? In the event of Chirstams you will receive a bunch of EXP like this Umufest. Since you may already have Cu Pro, I suggest you to use all Lancer Exp card for him during Jalter's download event in near future (super success rate of EXP increase doubled) then use EXP cards from Lottery for Jalter Lily.

How CUTE is Jalter Lily! Just consider her as little sister and I am willing to protect her against any harm. I wont put her in any challenge quest. Cu are much more handful for that.

Jalter is AOE, proto Cu is ST. If you already have Cu levelled, you don't really need to level proto, Jalter lily will benefit you more.