No this isn't right either. It's best to look at both. You also have to consider the equipment and materials available for forging and exp books. How are you supposed to build someone if you have 2-3 Fire girls or 2-3 ranged in one team? The best way to build a team is 1melee-1ranged-1magic and pick 1 for each elements.
I'm getting 7 shards/day in Isabelle's event right now. If you're really into it. Getting 7-10/day for 3* girls isn't hard only if you're going to use all your AP into it. Online twice a day will net you (120AP*2) 240 AP and if you do hell mode (30AP) then that's an almost guaranteed drop giving 8 shards. If you skip daily training then you can use the 50AP from friend gifting (+10AP regenerating while doing some random stuffs) for 2 more runs. Or add the feast for 30AP and you have 1 extra run. It's definitely faster and much more reliable than Trial Shop's 400pts (in which you need to beat the 10th floor for 430pts). And yes the more powerful 2* girls like Grace, Shalutta and Seleia comes with 400pts (cmiiw). If you fail then you need to wait for the next day. I'm pretty sure majority of the player base can't even reach that far. And for competition shop I think you mean 3 or 6 shards since I've never seen a 4shards/purchase.
650k battle power. My Trisha can easily destroy any mage (with 1-3 combo with same power) just as fast as your Elnora/Chharodi can kill her.
It's not all about element. You have to also consider Job Class bonus damage, their purple set (e.g. bane sets) and stats built. Sometimes two Elnora with same 200k power won't perform the same or deal the same output damage.
Also you forget that the OP of the question is just starting to play the game. So...
That's because you don't have a wind character, preferably a mage with archer's bane set. I easily mowed a 260k Chharodi in Tower of Trials with my 190k Elnora by just microing. Her attacks are so easy to avoid just by running in circles and her ult can be dodged by simply rolling. There's even no elemental weakness here. I'd be more scared of a Naladia because her attacks are homing and avoiding is simply impossible.
And even in with the same power in Arena, Naladia can fight toe to toe with a Chharodi despite the disadvantage with element.
9/10 of the player base are doing it wrong. Otherwise you would be seeing hundreds of announcements showing up. I'm also not using Claire (cause I don't have her) but some people suggested her (look at the previous pages forgot which ones). If you suck or just playing casual then why not try a complete turtle strategy. With the recent updates, even running around fills up the gauge so why not? 3 minutes is more than enough to kill all 3 characters with your hp completely in tact.
Every 3rd attack she shoots 6-7 arrows. It's the same way how Elnora shoots around 4 bullets on her 5th attack but way more efficient. Same with Yjer shooting tons of bullets. At point blank range it really hurts. You probably don't know cause you don't have a melee in the team you've given.
60k difference isn't enough to close the elemental weakness? Even 80k stings. So no, not entirely true. Other melees die a slightly slower death so yeah still it hurts. There's probably more into the damage calculation than a single elemental weakness. And as I've mentioned, my Trisha owns mages.
You're doing it wrong if your other two girls died and Isabelle was left battling a 3v1 match. This reasoning is flawed.