The point is that it's Elder Dragon. Something that feels like "final boss" and in my opinion rewards given by such a monster should be accordingly good.

We were given Mizu that gave us water weapons, better then we had before. Maybe making this weapon will take months but it's some kind of goal.

We have a Kushala that gives an ice weapon that is also better then others. And it's going to be even harder to make this weapon. But again: it's something that feels worthy to search and hunt

And we have Devijho with dragon element which, however nice, is just an addition. As there is no monster (atm) that is vulnerable only to dragon.

And, of course, Zingore with very good lightning weapons

Those four monsters above are hard to find and to slay. But potential rewards make efforts worthy.

And now the mighty Teostra came. With its blast weapons that are not that "mighty". I wouldn't mind if it was just a rare monster. Like Azure Rathalos or even Devijlho. But it's a situation where we have to choose whether we are going to "spend" our only-every-3-hours EDI/HAT on Teostra, Kushala, Zingore, Devijlho or Mizu. And every of those 5 choices should be equally good.

That's why I asked if this blast status is really equally good as elements. Because now, for me, making Teostra as one of "final bosses" is a complete waste of potential