Is woth rolling for Illya?

Depends if you want an offensive caster and like the servant tbh

She is a good ST NP Caster for nuking assassin bosses, but Xuangzang (who is in a story gacha permanently, not limited like Illya) does her job even better: can charge her NP gauge a la Medea, while Illya can't (just get some very minor constant bar increase passively), has a much better NP gain, and the best Caster 5* attack stat of the game (Illya is 2nd, whowever). Also, no demerit post-firing NP.

Illya still has a powerful mana burst-esque skill who will make her attack be way stronger than Xuang, yet she can't spam (or even easily charge) it as frequently; she can also give gutts to some1, but is chanced gutts (70%).

I will roll mostly for the 4* and 5* CEs (and potentially more 3* CEs, as my luck with FP gacha is horrible to get event CEs). Ofc, if I get her, I will raise her, is a 5*...

ps: For Sabers, for now try to invest on Caesar, decent ST NP for a 3*+ all his skills have utility for others (and himself). Yeah, Musashi is solid, but also 5*...will be kinda hard to get.

ps2: Why you dont try to raise a NP5 Hans? Quality support skills and NP, cheap on the party cost, cheap to raise skills...

What they said:

Level Hans. Do this for sure since he is the third best support out there and does multiple good things for the team and is very easy to np 5

Sumanai will be getting buffs so don't worry at least he'll be a par saber (no Lancelot but currently the only one par with Lancelot is okita).

Kuro is going to shore up your Archer ranks.

If you're still interested in an offensive caster though, do what I'm going to do and first try your gacha luck on memelin. If that succeeds or fails, wait to roll on Nero Caster in next summer event. She's one of if not the best offensive casters.

Unless you like lolies; then have at it with illya just don't be calling me for help when you hear a loud bang and the FBI have knocked your door down to arrest you

As a caster, Illya does the job well enough, but she is nowhere near the best for what she is - a single target offensive caster. As others have pointed out, Xuanzang is generally considered better.

Illya is basically good for 2 things: NP nuking and survival. While she has the highest burst damage of any caster, she can't use it all that often since her NP gain is relatively low. She also doesn't have territory creation as a passive, so her damage outside of her NP suffers a bit. If you're purely looking at gameplay reasons, I'd say give Illya a pass. Only roll for her if you actually like her.

As for Jalter, yes, she is absolutely worth rolling for. There are only a handful of avengers in the game and Jalter is generally considered the best of the lot. I won't go into why, it's pretty obvious. At least in terms of gameplay, she is a more worthwhile investment than Illya. Of course, I still have to stress that if you prefer Illya, you lose nothing by rolling for her over Jalter.

From what I've seen so far in some places she is usually seen as someone who isn't really good; she is a five star so still worth it just for the stats but the overall opinion seems to be that 'there are better options'

(Now that I said the serious part of my reply, here is the dumb part)

However, you HAVE to roll for her.

Now let me explain; it is not a matter of how good she is, it is not a matter of her been limited, it is not a matter of there been better options to save your quartz.

The fact of the matter is; YOU MUST REUNITE THE EMIYA FAMILY.

Seriously, you have everyone but her (and Kuro but she is welfare for this event so... that) you even have the family pet, Heracles!

Here is a short comic to motivate you (it is not mine, just to clarify): https://ar.pinterest.com/pin/AdIU_fCDNIMQeMJjdo0IKvnt9hxznl0VrM79xNFWPQs0MdFwxHiR124/

(all jokes aside, though, I think the best of the Caster class is the utility they can provide, even if you're facing an assassin Berserkers tend to outdamage the Casters, especially considering you have Herc)