Six mana allows you to turn all your creatures into X/Xs, which is of course a bigger upgrade if most of your creatures are very small, but its honestly not that exciting otherwise
While I think that Modern is better in general without free spells that can be used offensively, which gives me pause when it comes to recommending that Blazing Shoal be unbanned, I think the card would be fine on power level alone
The toolbox includes a set of damage counters featuring yellow 10-damage counters, orange 50-damage counters and red 100-damage counters
You want a bit higher count of removal and disruption effects than you might imagine as well, mostly because your self mill and dig tends not to find these cards so often
And those decisions are dependent upon so many other factors in the game
Unless, of course, you're relying on cards that let you play lands from elsewhere