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I’ve been seeing quagmire in the high rank elo, what do you think of him? 
I would rate him something like 3,5 depending on the map and what your opponent is using.
He can technically speaking be used as an annoying tank that can bully your opponents early game on larger maps - But where he really shines is as a frontline in the mid-game followed with some decent ranged units since he has a big health pool (makes it hard for the opponent to engage on your lineup without losing out on the following turn, which means that you can use him to slowly pressure your opponent off the map to take over Panic Point control).
His main weakness is also his biggest strength though: He’s just a tanky guy with melee attacks, so if he doesn’t have backup your opponent can just kite him with ranged units and only let him hit once per turn. (which is why he needs to be backed up by other units).
in my opinnion
It is overpowered in small map. with maximum unit of 5 you either have to sacrifice something or really really have to be sneaky cause his large pool of health. he can just take all the shot you have in low key phobies and probably still alive. if he’s alive he can just regen at the back. i can say his big pool of health is not that big of an issue but the regen is forcing you to either commit to kill it or let it alive and play in distance. if you and your opponent both have quagmire then good lord it could be quite a stalematch. he’s cheaper alleygator that can pressure a lot especially in early. while your phobies find themselves focusing on the quagmire, your opponent’s focusing on your phobies too. it doesn’t have mobility but it does packed a punch, and in smaller map, sometime mobility is not the main concern. and if you try to save up more keys, the opponent’s phobies might have conquered your panic points or already arrived at your heart. invest in push or pool phobie
On big map, kinda alright and if you’re lucky you can kite it but that kinda rare cause everyone seems to play turtle with this tank. i don’t see the point to spawn quamire at late game cause you might need to spend the keys to counter what your opponent doing. and there’s a lot ofn5 keys phobie that has better benefit depending on the map and also since big map give lots of keys, you probably can spawn something that can murder it without sacrificing anything, or better, push/pull it to the cliff
now to counter it…
do not yolo your sheeping gas to poison it. if he ran away he can outlast your poison. unless you are sure that is 1v1 and later on you can catch him (pray that he die before clinico areived)
Traps would be nice cause it trigger after he heals, less damage you need to deal.
commit whether you want to kill it or feel safe to play distance
boost pad is a friend, also push/puller phobies
I’ve found that Quagmire’s effective on small maps, and is best for stalling to get some keys. Really good tank unit. 4/5. Would recommend for beginners, honestly my most used unit. Edit: As for its cost, perfect, not too cheap, but not too expensive. Usually I counter with Sheeping gas, and 2 of any cheap attack units with damage greater than 500, like Wiggy and Maggie. Really useful early game with or w/o support. Usually I use it as a distraction while I amasse my phobies in the back-lines, or I put some ranged phobies like stabby and murder wing. Another strat for bigger maps is to curve the phobies around the sides and make a pincer attack.
I usually bring Quagmire in early game because he can 2-shot every 1 key and some 2 keys. also he can regenerate really quickly and if paired with Clinico then he is really hard to kill.
Also he looks cool 
personally i admire this guy. try to play him often. I mostly use him to capture Panic points of the enemy, where he will survive retalitation. also a very good meatshield for your ranged units. i play him a lot. adding his occasional +400 heal ( i don’t have the level one stats in head) he most likely will stick around until the end. or you sacrifice him to the enemy who has use most likely all his capacities to kill him before he again would back up allowing to secure another part of the map. to be honest he also works kinda fine with cecilia to bulk the enemy away
I prefer him over alleygator
to counter him i have to look at the rest of his rooster. because like other ones mentioned he’s in the end a meaty melee combatter with not that much of a damage output. meaning there some guys , especially melee zombies have a good time to bully him. on small maps he’s a fixed slot if spawned. if he healed him with clinico this would be 2/5 melee attackers. you just might walk through him and ignore him completly, depending on the map.
wooly bully also shuts his damage output down
enemies also tend to play rusty in my case against him. i don’t have this guy. deseasing him also might help if you’re capable too. and have bigger numbers then this heal. if his crew has few to no bots and/or poison disease spreaders fowl disrespects him completly.
the guy mentiong the traps has also throw a good hint. poison ivy or especially lila gives him hard times, but the fungy guy is also one i miss badly in my rooster.