the gameplay is alright but it's extremely tedious. it took about half an hour to beat the first lvl. with the battles being so long it seems tat thre are so many lvls to go through.
i know your relying using the various heroes to try and diverseify gameplay but it takes a little while to even have the ability to use your hero in the first place. which means that early game everything follows more or less the same pattern of rushing basic mellee and ranged units. and even after you finally get to use the hero it is only really a support anyway. i don't know about the other heroes but as the big warrior character all you had to do is use the stun and knockback abilities and you can more or less push straight to the enemy base without to much trouble.
the bases themselves are the biggest reason for the length of the games as they regenerate health over time. which means even after pushing to the enemy base you really don't do to much permanant damage, as the turret will decimate your forces with ease. theres no real point in pushing till you get the catapault anyway since your base also has regen and it's own turret. all you need to do is repel the enemie until you can get your catapault at which point you can just use all your money to send a constant stream of units to your enemies base as your catapault pounds away at the enemy tower.
the spells are pretty intresting, though the lengthy cooldown more or less stops them having much effect on gameplay. i do like that the enemy has spells too even though they get them too late to make much difference.
sry for the long review ^^; hope it helps a bit