Updated: Nov 30, 2021
Some tips on Hero set-ups for tiles. There's some misinformation floating around that Forsaken in the front row is god because of his skill 5 Silence effect. This is incorrect, as Silence does NOT help against Zombies. Silenced is "unable to use skills" which only Heros have, and Zombies don't have any skills. What you want, in my opinion, is Suppression. Suppression prevents normal attacks, which the tile guardians have. As such, this should be prioritised.
Now, for pushing higher level tiles, the best set-up is Captain Ivanov, Major Anastasia Nastya, and The Panther. Ivanov in the first position, Ana in the second, Panther in the last spot.
The reason this works, is burst damaging on the first round of combat, before the poison damage kills all your troops. You don't fill the APC with 100k troops in each row, you only need 20k/30k in each row, maybe more depending on your level of tech/parts/hero skills.
Ivanov's 8th skill gives +80% damage, and his 2nd skill has a 40% chance to double attack.
Ana's 5th skill gives a 70% chance to give friendly squads (Ivanov) double normal attacks, and her 8th skill has enemies take 12% more damage
Panther's 8th skill has 70% chance for the front row vehicle squad to counter-attack when attacked. 5th skill gives 70% chance to splash damage to enemy rows 2 and 3, and 2nd skill gives 80% damage increase for friendly.
Now, obviously. the ultimate set-up would be enhanced T9s, with a Baneblade parts, and maxed hero's, and maxed technology. Of course, not everyone has this :P
Even with gold parts (Phantom), and not maxed hero's, this can still be a solid APC.
Assuming the percentage based skills trigger, Ivanov attacks first, with heaps of damage bonuses, multiple times, and splash damage to second and third rows. Then, when the Zombies attack, he counter-attacks again, with damage buffs, doing more damage. When the round ends, and the poison kills all the troops, and the battle ends, you should have done enough damage to win the battle, and defeat the guardian.