It's good that you finally have time to make the combat portion of the game more interesting. I haven't really played this game for almost a year now, but I have been following it on Steam and Twitter so here is my yearly megapost:
1) Do you really need so many types of damage? All MOBAs that I know of only have Physical, Magical, and "True" damage, and true damage isn't a proper damage type like the other two. Even Kingdom Rush only has normal and magic damage, and I think it is a fairly complicated tower-defense game. These games do have armor systems, however; normal armor reduces physical damage and magic armor reduces magic damage (true damage bypasses all armor, but true damage is usually just used for on-hit effects and such). Personally, I think that one damage type is enough, but the various attack types can differently affect the statistics or the status of the target
- A = attack value
- R = armor of target
- H = health of target
- H_max = max health of target
- S = speed of target
- S_max = max speed of target
On-hit effects (enemies are susceptible to all on-hit effects unless they are explicitly resistant).
- Ignite - Targets that are ablaze slowly lose H until they are dampened
- Poison - Poisoned targets slowly lose H; poison rapidly clears
- Infect - Infected targets slowly lose H_max; infection rapidly clears
- Dampen - Targets cannot be set ablaze and take double damage from electric sources
- Slowed - Slowed targets have reduce speed; slowedness rapidly clears
- Blunt: H -= max(0, A - R) // Flat damage reduction
- Pierce: H -= A / (A + R) // Fractional damage reduction
- Cut: H -= if (A - R < 0) 0, else A // All or nothing
- Lightning: if target is wet, H -= 2*A; else H -= A
- Fire: H -= A; ignite
- Water: H -= A; Dampen
- Acid: R -= A
- Poison: H -= A; poison
- Disease: H -= A; Infects
- Ice: H -= max(0, A - R); Slows
and so forth
The point is that I think it's more of an interesting puzzle game when you play around with stats and effects like this instead of just matching damage types to target types. In particular, I think the order in which towers are placed becomes more meaningful. There are also Strength, Intelligence, and Dexterity stats, too. Are these going to factor into the damage calculations?
2) Will we be able to disable towers during battles? It would be nice to have some tactical input during battles rather than just to watch things kill each other. Since ammunition and essence are temporarily limited resources during night time, disabling towers that kill poorly while enabling towers that kill well would be a good idea I think.
3) Are you still going to let enemies wander around during the day? This game can only handle so many mobs at once and I don't think it's a good idea to rely on the player to kill stuff in order to keep the mob count at a reasonable level. Rather, it would be easier to ensure decent performance by killing things off during the day and then spawning a reasonable number of them at night, making them more powerful instead of more numerous as the game goes on. I know this has been suggested before but performance was still a problem the last time I played.