Last I checked Runic Blade does not confer Barrier to your party, and only works in one specific set of circumstances. Let’s go through the best cases.
The best-case is you manage to kill the DB-bearer. It’s generally in the 1st slot and a fairly strong hero so for this to pan out you need:
- 2-3 rounds of skull damage -or- an activation of an ability that can knock the DB-bearer to ~14 HP.
- Collect enough mana to activate Runic Blade.
- Do the above before Dawnbringer activates.
Timing is very tight. If your board doesn’t start with skulls or isn’t yellow/green friendly, you’re hosed. This case almost always ends in a win, but you can be blocked from it by luck. No amount of skill makes this a high-probability case.
The next-best case involves:
- One of the defense troops can be killed in one RB activation (smart DB players avoid this). -Or- something is very close to that HP.
- You have a cheap, targeted damage-dealer that can knock a non-hero troop to Runic Blade range.
- You get to collect enough mana and spend a turn activating that damage-dealer.
- You get to collect enough mana to activate Runic Blade.
- All of this happens before Dawnbringer fills.
If you pull that off, your odds of winning are higher, but there’s a problem. A Dawnbringer activation will be close, and odds are afterwards you have a weakened hero and maybe 1 troop vs. 2-3 barriered opponents that still have Dawnbringer.
All of this is quite difficult. You’ve got a 2-3 turn window to work with, and if the following are true you’re going to take a DB hit no matter what:
- Sometimes the board is not green/yellow friendly. Dawnbringer collects other mana so it doesn’t care.
- Sometimes the board isn’t friendly to your damage-dealing troop. You can fill Runic Blade but it has nothing to kill.
- Sometimes you don’t get an appropriate damage-dealing troop in the entire draft.
That is, overall, bad odds. I don’t like Arena having a weapon so powerful that facing it and winning involves having drafted a specific team AND having luck. No other weapon affects how I draft so significantly.
No one can make the argument, “DB is unbeatable”. The argument is “DB is powerful enough to cut the win rate enough to make the game mode feel uninteresting.”