Trickle Down Balance

Gamers (and unfortunately developers) too often submit to this fallacy:

"Game balance is best achieved by looking at the pro/tournament level. Any balance there must necessarily trickle down to all elo tiers"

This is, quite frankly, false.

Some mechanics provide windows of opportunity for counter-play - if I press the button within 1 second of you pressing the button, I win, else I lose. The better the reflexes, the weaker in power the mechanic.

Skillshots: harder to dodge if you're less skilled

If the correct counter strategy is too sideways or hard to intuit, a strong player will recognize it more readily than a weaker player (who may not see it at all).

Not the most immediately obvious tech to beat the guy casting Cruel Ultimatum and Knight of the Reliquary

The road goes both ways. Skill barriers can also be critical points. A mechanic requiring some base amount of skill may be overpowered in high-level play but meaningless in lower-level.

Sniper Rifles: the classic video game device whose power multiplies the effectiveness of the player looking down the scope (for better or worse)

Sometimes competitiveness is more relevant than skill. Unspoken or house rules may prevent me bringing my Affinity deck to the kitchen table every night, but that doesn't mean Arcbound Ravager isn't going to get the DCI banhammer.

Katarina Mid-Death Lotus

League of Legends is a game offering a wildly different experience depending on your elo. Katarina is extremely binary - she either murders the entire enemy team with her ultimate or is stunned immediately and is worthless. An unskilled or uneducated team may not have the necessary tools to interrupt her, may not recognize that that is the correct answer, or may simply be too uncoordinated to react in time. A pro Katarina on the other hand will never use her ultimate for more than 0.5 seconds before Alistar Headbutts her. While weak at high levels of play she can quickly snowball to dominate in the lower elo.

Urgot, the most top-less champion

Urgot's kit of synergies and skillshots has the opposite problem. A good player can fire 3 locked-on Acid Hunters and can Capacitate his Terror at just the right moments. At high enough skill levels he is powerful enough to see routine bans. But in lower tiers he's seen as merely fair or even underpowered due to his poor late-game scaling.

In Magic this tends to play out not by skill but by how casual your playgroup is. Hermit Druid can be a nice card advantage engine with an unrelated downside, or it can degenerately end games on turn 2 by knocking your entire deck into your graveyard. House rules are usually enough to deal with this without resorting to the banhammer, letting you run Panoptic Mirror as long as you're not "being a jerk". But when we play with strangers we need a banlist and that list must by necessity look to stop all the things that make the game not fun.

Every casual Starcraft player has at one point Attack Moved these and giggled maniacally

I remember back in the day thinking "boy are Carriers overpowered". It didn't occur to players at my skill level (i.e. "poor to none") that the correct strategy to beat my killing machines was to send in 4 Zerglings at some point before the 40 minute mark. High Templars on the otherhand always found themselves in an Archon sandwich - "they must be useless, they can't even attack!" - but I know the number of Psionic Storm casts in tournaments far exceeds the number of Interceptors produced.

This isn't something that will ever be fixed. Games will always have disparate skill levels which affect their experience and ability to optimize. Mechanics are only as powerful as the player controlling them.

But this can't be swept under the rug either. League of Legends is not balanced once each of the N champions are played in 1/N of tournament games. It's important to look at the balance for each level and ensuring that if the game is not the same then at least each subgame is fun. You may even want to recognize which players are more important, and while tournaments are the most widely viewed they are also the smallest actual player base.

And making each aspect of your game fun is a balancing act.