But you're completely ignoring all of her skills that she has easy access to (i.e. she doesn't need to reach a certain support level with certain characters to get them, meaning you don't need to grind much for good skills), most notably Copycat (which is the ultimate tank skill, like she could have OK-ish Defense and Speed and still make a good tank with this skill. Good thing she has good stats in both), her Personal (which basically averts her low Str because if Rinkah isn't on the front lines and taking hits then you're using her wrong), then things like Death Blow, Lethality, etc.
Copycat is in no way a tanking skill(the name is Replicate actually), it gives you more offensive power but since the copy shares current HP with the original it means you can be attacked way more than normally
And anyone with access to Ninja or Apotechary can get it, it's nothing special(Kaze, Saizo, Kagero, Midori, Asuhi, Shura and anyone with those classes as their secondaries)
Counter is the one tanking skill she gets at her base classes
And honestly her HP and Str are perfectly fine.
No, they're not, 20% HP and 25% Str personal growths are terrible
At worst, you just give her one of the permanent boost items for those stats and she's fixed.
There are characters that would take better advantage of those items such as Sakura and Azura for the Angelic Robes and any other physical offensive unit
I also don't really care about how she compares to Conquest units, at least not in the context of just going through Birthright's story.
The three examples I mentioned are all avaible in Birthright
Silas and Jakob are shared between versions and Scarlet is BR exclusive
They're also all more mobile, strong and durable, they completely outclass her on everything but maybe Res(which isn't as useful when you don't have many magic enemies)
but the designers of the game probably did that because Conquest has limited grinding and therefore the characters need better stats from the get go, compared to Birthright which is more customisable and flexible in terms of how you can build units, so base stats are much less relevant.
That's not an excuse, especially if you see how badly unbalaced Revelation is, just because there is grinding doesn't mean they can have bad bases
Rinkah has bad growths on top of her bad bases
And the grinding just speeds things up or allow the abuse of Eternal Seals, Conquest's characters can reach 20/20 easily with no grinding
And no, it didn't require extra favouritism to get her to where she is now
Feeding her stat boosters, giving her a special class seal, using various Heart Seals on her and leveling her to the point she almost doesn't get any experience IS favoritism
Any other BR unit would turn out way better than her with all this treatment
It's not like you should do that because certain characters take advantage of those items better(Azama and Kaze are the prime candidates for the Dread Scrolls in Birthright, as I said before, Azura and Sakura make good use of Angelic Robes and Jakob 1, Corrin, Kaze, Saizo and Hinoka all make vetter use of the Heart Seals)
It's like I keep saying, people who don't use Rinkah and especially those without Birthright will assume Rinkah is terrible because of first impressions
First impressions in FE are a character's bases, if they don't have good bases, they need growths to make up for it(like the Est archetypes), Rinkah doesn't have neither and numbers don't lie
But people who actually stick with her will see the potential she has early on and will want to stick with her. And it really didn't require going out of my way that much (keep in mind this is my first Fire Emblem game so I'm mostly just winging it. I only learned about Rinkah's great skill set and what not because I wanted to look up some things, as I was a bit confused on how stuff like re-classing works at first, and I needed to find out if you could get Dread Scrolls normally or if it was a Path Bonus exclusive). The fact that I have Dread Scrolls means I'm even better off than most people who want to use this character.
Being your first experience with FE isn't a good argument since your first experience is with the easiest game in the franchise
I could throw units in the middle of a bunch of enemies in Awakening Normal like it was nothing but that doesn't mean they're good
A character that can achieve a 100% Crit and Hit Rate,
Beruka and Arthurs says hi
has easy access to Copycat (which is one of the most broken skills in this game),
It's broken in multiplayer because of the 5 unit limit, it's a double-edged blade in the main campaign
offers some of the best Support bonuses,
That's what we call a pair-up bot
and can take hits and dodge hits with ease even on the hardest difficulty in a game where barely anyone else can,
You're playing a game where you get 3 Samurais and 3 Ninjas, don't come with this "no one else can dodge" bull****
Also, she takes hits just as good as Hinata does