Some towers are not particularly useful (in high lvl gameplay) currently - mainly useful now are only skull tower for its raw high area damage and boosted bomb tower for its long ranged area damage (plus firebolt for its “immunity” to melee damage).
Some of them lack range (frost, gargoyle, snake) and can thus be destroyed either by any ranged troops and bypassed by the king and/or troops mostly unharmed, or quickly destroyed with a spell without any prior damage being dealt ahead of time before the short moment of casting the spell. Slightly extending their range (at least on high/max lvls, like has been done e.g. for the firestorm spell as well) to match at least those of the shortest ranged units (archer 3.5, gargoyle 3.5) and also cover a whole path tile to make it impossible to bypass them unharmed, might make them a lot more useful.
Fun fact: Gargoyle tower description says those make a lot of damage against frosters, but due to frosters having twice their range, they will never receive any damage from gargoyle towers at all.
Some of them lack a decent progression of stats when levelling them up. Most upgrades for towers, troops and spells are roughly+20% health and damage per level, so +20% is the regular/normal progression rate for stats. This makes lvl 9 about 4.3 times as strong as lvl 1.
Gargoyle tower and (since an update that buffed lvl 1 by 65% and nerfed lvl 9 by 5%) firebolt towers are two examples of very low % improvement upon upgrading them (between 10% and 15%), despite the general cost and/or cost progression for upgrading them is quite high.
A lvl 9 gargoyle tower is only 3 times as strong as a lvl 1 (compared to 4.3 times as strong for average/normal progression).
A lvl 9 firebolt tower is only 3.1 as strong as a lvl 1 firebolt tower.
This makes them decent/useful at low lvls, but the gains from upgrading them are too low to be worth upgrading them to max lvls, thus making them more and more irrelevant altogether the higher you get (yes firebolt is used in some top bases, but only to waste a spell for making sure you don’t end with 98% when your melee troops can’t hit it, and not because of its stats). The last few arrow tower upgrades btw also have a lower than average stats progression.
Some towers are just too weak (low health and damage) but also relatively cheap, and could be more useful by adding another lvl or two, increasing both total cost and max lvl stats (e.g. arrow tower).
What do you think?