Why is (orignal) Sakura's Guide is waay to outdated??

If her guide is outdated (I haven't checked) then it might be because people forgot about her.

As for why she's tier 5, I really can't answer that. Tier lists are opinionated, so unless you change the opinions of someone that made the tier list, then chances are they won't be changing their stage on the tier list. Could have something to do with the fact that she's an infantry healer? Again, not really sure.

healers aren't very good units for tank builds and sakura's balanced stats make it hard for her to specialize in anything so as a tank, she wont be on the levels of units like azama and lucius.

people also dont build healers with close counter very often so their defense is not something they would look at. So a unit like Serra who has more res(+3) and more speed(+1) has a more optimized stat line to be a healer in exchange for less defense and HP as well as 2 more points in attack. She's also easier to build because her specialized stat line allows her to build hyper offensively more easily that Sakura and has stronger heals because of a slightly higher atk stat.

in general, Gamepress' Tier List favors hyper offensive units (with the exception of armor units and units with prf weapons and exclusive skills like sigurd). You can see this when you compare a unit like Raven and Beruka. Beruka is a godly unit if you build her right but she only has one build that really brings her up while raven can run multiple different builds and can perform well in all of them.

just because gamepress ranks them low, that doesn't mean they're bad. it just means they need more support or more expensive skills than others.

My only healer I invested in so far is Sakura lol. I got one with +Atk -Hp and decided to work with her from there.

I run Dazzling Fear+, Physic+, Miracle, Attack +3, Wrathful Staff 3, Savage Blow 3, and Savage Blow seal.

She's just a pretty fun unit to work with imo since she has some decent bulk and some decent offensive stats too. I can see why she isn't top tier, but I don't think Tier 5 seems right.

I really like your Sakura, and I wish more people would build her. I personally like Sakura and don't think that she's bad. Actually, I plan on building her to +10 (if I can ever pull one with the IVs that I want, or any for that matter). Anyway, I'd imagine that people consider her really bad as a Staff unit for these reasons:

Mounted Healers are just too good. They get access to Cavalry buffs and have more movement. By default, they will always be better than Infantry Healers, unless IS decides to release one that is just super crazy.

Below them, the other Healers either have high Atk or high Spd (or both), which allows them to avoid more doubles, or heal more HP, or deal more damage. Then, you have those with natural access to Pain+ or Gravity+, which are great staves.

Sakura, while having a very solidly balanced stat spread for a Healer, doesn't excel in anything. She also comes with Fear+, which is good but not as crazy as the other two, especially when Atk Smoke is available in seal form.

Underwhelming balanced stats, not enough speed makes her defenses paper thin, very low atk. She's a very underwhelming unit due to a lack of specialization.

Yes, your Sakura can one round an Ayra or Zelgius, but you require Swordbreaker, an atk boost, a summoner support boost AND wrathful staff. It doesn't help that Staves generally do low damage, so they're mostly better off being used for utility rather than raw damage.

To this end, Serra can do slightly more damage per hit, and has 1 more speed. This gives her slightly more utility in general, if only in a minute sliver of a difference.