Swamp Mirrorer is very good for E Hero deck, because you can use it as fusion material for Nova Master, Gaia or Great Tornado simply by choosing the correct attribute. Also you can fusion summon a 3400 ATK Neos Knight using Swamp Mirrorer (choose WARRIOR for its type) + Neos / King of The Swamp / any fusion substitute. Neos Knight cannot inflict battle damage but its high ATK can swing into Anki or even Blue Eyes
Still E Hero deck sucks because it needs too much stuff to summon a monster just to get floodgated, Canadia or even Treacherous. Konami give Aster a 🔥 quick-play spell that needs only one tribute and a boss monster that can search the spell from the deck, please give more love to Jaden by releasing Stratos / Prisma / Absolute Zero
And they gave him some of his good vision hero stuff. They need to give more e-hero support as well so that they don't look like they are playing favorites. And...because Aster also uses elemental heroes. lol Let's start with the cards you mentioned and the phoenix enforcers.
Starting with probably the strongest Elemental HERO cards in the game... What would you even escalate to after that aside from Shadow Mist and E - Emergency Call?
The only stuff we lack that we'd have a legitimate chance of getting that would actually be used in E-HERO is like The Shining, Emergency Call (as a level reward) or Mirror Gate.
We're likely not ever getting Stratos, Prisma or Grandman.
Hero Blast will likely happen eventually. I guess triple Emergency Call might happen, but I view Diamond Core as an exception, not the rule. Absolute Zero might, but I doubt it.
Brave Neos might happen, but it isn't super-useful outside Neo-Spacians (still generic and can search Miracle Contact to Summon another, so might be worthwhile).
They are milking out the heroes (mostly the e-heroes) for as long as they can because they know that a lot of people will be willing to get them out of multiple boxes. Why are they so afraid of mirror gate and phoenix enforcer/s? "Can't be destroyed in battle." Big deal! How often does that even happen now? And it can't revive like amazoness queen.
"Koga" and "Goka" are different. We already have Goka in Duel Links, it is a trash card compared to Anki. But Koga is different story, it is a very good card that deserves to be a UR if Konami decide to release it in Duel Links