Is it worth waiting for Jeanne Alter?

Straight Answer: In depends on which servant you want more.

Complex Answer: This game doesn't rely heavily on very rare servants in order to beat most of the contents that the game has; lack of good 4-5 servants just makes the process harder and sometimes strenuous (Like Camelot and latter stories and events that is hard to beat. Camelot is hard without thought out strategies for each quests).
HOWEVER, the reason why we pull for servant is simply because you want them. There are people who pulls for Enkidu and other "bad" servants because they like the servants' characters.

But I guess you're asking in terms of lack of lancers in the deck currently. In terms of getting 4 star lancer, Lantoria Alter is a great choice to pull if you really are struggling by lack of good lancers since she is one of the best 4 stars and the best 4 star AoE NP lancer to use in the game even for the later part in the game. In my opinion, it is better to pull for her than Karna (a new 5 star lancer servant coming out in probably New Year) since she's a 4 star and is most likely easier to pull her than 5 star Karna. So if you don't care much about JAlter and cares about the stronger servants, then sure.

HOWEVER, if you are willing to wait for few months, pulling for JAlter would be a better option because JAlter is one of the best servant in terms of servants' offensive capabilities. She does insane amount of damage with the right buffs and is very versatile in many situations. The fact that she is an Avenger helps her to deal well since she gets 1.1 boost for her attack. If you are willing to survive archers with Support Lancers like Friend Scathach, Lantoria Alter, and Karna in the future, then I suggest you to wait and pull for JAlter with your saved or paid quartz.

SO, in comparison...
Lantoria Alter for...
1) 4 Star - easier to get than 5 star
2) One of the best AoE lancers in the game even compared with some 5 star lancers
3) One of the best lancers in the game in general imo
4) Very respectable Waifu (if you care about waifus).

VS

Jeanne Alter for...
1) Best servant for Offensive measures
2) Avenger class gives 1.1 x her attack
3) Versatile in many situations
4) Again, Very respectable Waifu (One of my favorite Waifus in FGO)

In conclusion, it depends on what you want for this game.
4 star Lancer waifu with Strong AoE NP and one of the best lancers in the game? Lantoria Alter is your main pick.
5 star Avenger waifu with Strong ST NP and one of the strongest-hitting and versatile servants in the game? Jeanne Alter is for you.

Since I can't perfectly explain what they are individually capable of, I advise you to do more research, but at the end, pull the servant you want the most. I hope this reply helps. Any other questions, please ask them on my comment.