you know how rock paper scissors works? of course you do, but some might not so let me explain
there are 3 choices and each choice is weak against the choice before it and strong against the choice after it.
like this - rock --> scissors --> paper --> rock
rock paper scissors is actually not balanced
in order to achieve balance there has to be equal forces on both sides otherwise you're not achieving balance. balance would be playing rock paper scissors with just rock to choose
rock=rock
in video games we like to talk about balance a lot, but what everyone actually means is strategic advantage. especially when playing a game that is about taking advantage of your opponents weaknesses.
strategic advantage is something a bit more complex than balance and requires a great number of variables to be enjoyable.
take a game like pokemon for example. if we use their type system we get a couple of different effect cycles that provide simple advantages and then there are effect constants that provide complex advantages.
the basic element type cycle :
fire --> grass --> water --> fire
then there are advanced elements :
ice and electric
these elements do not follow any particular rules, but seems to be designed with the idea that it is the inverse of a basic element such as ice - fire and electric - water.
ground, rock, and steel
these elements were likely designed as an afterthought for balance with steel not showing up until generation 2.
and variables like :
flying or not flying
ghost or not ghost
dark or not dark
dragon or not dragon
fairy or not fairy
fighting or not fighting
psychic or not psychic
poison or not poison
bug or not bug
normal or not normal
these variables can stack onto other combinations and have a simple function of negating out as much of the basic elemental damage advantages or in some cases other state variables.
in a game like league of legends though the stats are the elements that make up the strategic balance
currently those stats are all over the place.
each champion is effectively its own variable and with stats being everywhere the game is neither balanced nor does it provide any strategic advantage.
no matter how strategic advantage is implemented in a game like league there needs to be a balance between offense and defense.
currently the scales are shifted towards offense.
changing the name of some champions to warden vs juggernaut doesnt help with balance anymore than calling fire pokemon infernal pokemon. it focuses their kit on a single element of gameplay, but it doesnt fix the offset of defense vs offense nor does it correct strategic advantages that are overbearing.
if we look at all of the strategic elements of league we get something that looks like this
ranged vs melee
offense vs defense
magic vs physical vs true
ability vs basic attacks
cooldown timers vs attack speed
movement vs movement effects
health vs health regeneration
resources vs resource regeneration
critical multiplier vs no critical multiplier
every item, spell, mastery, rune, and ability in the game is either offensive or defensive and grants one of those variables. it can be a multiplier or an additive constant, but unless the total of the champions kit plus any combination in the game is equal to 0 in terms of value when compared to all other champions then that champion is unbalanced.
unbalanced champions will be exploited for their positive values and forgotten for their negative values.
this is a matter of mathematical inconsistency and the best way to improve the chances of reaching a balanced point is through simplifying variables before trying to combine them.
http://www.reactiongifs.com/r/2013/05/didnt-read.gif
TLDR
in other words creating more variables by creating more diversity in roles will cause even more imbalance and a feeling of lacking strategic advantage due to that imbalance.