SSR rate is trash at 3%. (then you gotta luck out on rolling a character or lucifer/bahamut...) Wait for legendfest where rate is doubled to 6% if you want it to be more bearable unless you really like Slayers.
Rerolling isn't necessary but it improves overall game experience, you will get your SSRs eventually. If you feel like giving up and just enjoy the game there is no harm with it.
I don't have any SSR characters and got Macula Marius from a single pull. It hasn't really mattered at all since I'm not actually sure what benefit there is - my main three characters are Anna, Catalina and Elmott and they're all a minimum of level 40 but their actual damage output seems to depend on what weapons I have so I'm stuck taking on quests that are only difficulty of 9 or less.
Not sure if any of the mods still support this community, but they should be aware that the forums are infested with bots and that their forum needs to be upgraded.