Do you mean unit effectiveness like in rock-paper scissors, or units only usable on either attack or defense, or both?
So true… since the introduction of the first elite boosts 9 months ago or so, I don’t remember a single time where I really used several different combos for attack concurrently, because all the time there’s like exactly 1 very effective combo, with maybe 1 minor alternative for one single of the three troop slots, and everything else is just completely useless on (high lvl) attacks.
The by-far biggest changes to my raiding combo during the last half year or so have been substituting “knights” with “mummies that spawn knights”, after war boosts came out (dominant combo changed there), and switching from wolf to cannon when wolf was bugged, and then back to wolf (change to adjust to / minimize harm of severe gameplay bug)…
The remaining “diversity” between raids currently is mostly limited to “should I use more/less of mummies and knights or archers” at a certain point of time during the raid. And of course, even this minimal “diversity” is no real choice but rather a means of being able to survive and complete a raid because one of the two possibilities for balancing your troop spawns is more effective at a certain time/base.
I mean, it’s a challenge to beat high lvl bases, so during a single raid you definitely don’t have time to feel bored, but overally it’s very boring to have to ignore like 98% of all possible combos for spells and troops, while always using the same single combo all over and over and over again… basically it’s just endless grinding smashing the same troops against not identical, but still very similar bases all the time, repetition of one best-option pattern. Sure, it takes some skill and time to practice that pattern, and on every raid (especially against unknown random match maker bases) you have a risk to misfire a spell or two, most probably failing the raid unless the oponent is comparably very easy, but all in all it’s just, with one word, repetitive.
The largest amount of variance currently is slightly different lvl of defender’s waves, and some bugs/glitches affecting movement speed and damage dealing, which sometimes makes you lose the same identical base you just before easily won. E.g. I did 3 subsequent regular raids on 1 player within 5 minutes (and he was offline, or I couldn’t have attacked him, so definitely the base didn’t change during that time), 1st raid (base unknown before) was easy 100% with 15s left despite I had slightly misfired 2 or 3 spells, 2nd raid was timeout at 67% despite better spell timing and some knowledge about the base, 3rd attempt was timeout at 40% with better knowledge about base and better spell timing than on 1st raid. And this example, while it may sound extreme, is 100% true, and is not the first of its kind either, but rather something I have come to generally take as a given - especially after months with bugged spells and units, which made raiding outcome mostly random anyway.
Anyway, back to original question, more variety is necessary. And not just “let’s add a new unit or two”, but also (mainly) balancing existing content to give more viable, equally strong options for combinations of troops/spells/towers.
Only thing I don’t want is “more boosts”, mainly because it only increases pressure (both on alliances as a whole, and on individual players) and pay2win, and also because looking back at the last year of RR2, boosts didn’t really make more viable options but rather less…
E.g. boosted paladin is still as useless as unboosted paladin, for high lvl gameplay, while (as only remaining unboosted troop type for higher level bases) the froster is more dominant than ever before lately, which in part is due to changed attack combos, and partially due to bugs/glitches/secret-unannounced-buff(?).
Mummy as boosted tank replaced both ogres and, for the most part, wolves.
And buffed froster and arbs, together with mummies for offense, made cannons mostly obsolete for top bases.
First season of boosts made formerly widely used arbs useless thanks to boosted archers, and even boosted arbs are now (on offense) rarely ever used.
Troops like pyromancer or mortar were getting useless with introduction of boosts as well, and still no boost for them made.
And of course, all the boosts complicate balancing, because both boosted and unboosted versions / levels should be balanced.
And as generally only high lvl paying alliances can even afford boosts (making them mostly irrelevant for large parts of the community while at the same time they’re essentially necessary for bare survival on the higher tiers of the game, where most veterans and also most big spenders reside), this gets even more complicated: Whenever working on improving the situation, they ever ignore most overall players by balancing the boosts, or ignore most veterans as well as most big spenders by working on something else.