Game Maker is a tool, and like any tool, you can use it well to create fantastic things, and you can use it poorly and make utter trainwrecks. The fact that I'm explaining this means you probably know what side of the line Hero Siege falls on.
Hero Siege wants to be Diablo, on a basic level. It wants this BADLY. It breaks itself into 'acts' (with a new, fifth one in DLC form!), it has a bunch of classes with skill trees of their own, it involves semi-random world generation, and loot plays in heavily, with a smattering of crafting. Heck, it comes as close to ripping off the Diablo font as one can without a C&D being involved (if it's not actually just stolen outright - I haven't compared directly). The big problem is that the game's everything is a muddled, broken husk.
The gameplay isn't mouse-based, and in fact, the mouse barely functions in the game. It's more like a twin-stick shooter, except you only have the four cardinal directions to work with (you can combine them to move diagonally, but if you can fire diagonally in any way, I didn't get it to work). Random 'traps' appear on the ground and around the world, and this is problem number one: the art doesn't convey things well. Things which appeared to be scenery would suddenly spit out a bullet and BAM, half my life gone. Even worse: bullets don't appear as the top layer of graphics, meaning they might hide behind other objects and suddenly go right through you. Instead of exploration being key, you're mostly in arenas which spawn enemies in waves. Sometimes you spend gold on items between, or level up with an incredibly pedestrian character skills tree here and there. (Fun fact about the level up screen: tooltips do not always work, so have fun figuring out if something is a trap or not!)
To top it all off, this week there was DLC released for the game, which adds multiplayer. "Early Access" multiplayer, according to the in-game menus, but really the entire DLC is half-baked: for most of us, it doesn't work. At all. You can purchase it but if it doesn't allow you to unlock anything? Well, according to the devs, that's Steam's fault. It totally happened to a dev's copy of Indie Game the Movie, so that means they didn't code things poorly, you guys. (This is an actual excuse.) You don't want it, just like you don't want this game, but I really figured the technical problems were best summarized by that. Or the fact that options don't save/kick in unless you visit their screen, in which case it remembers "Oh yeah, you turned the volume down" or "Oh yeah, I'm set to Windowed mode!" and suddenly picks up on the thing that it saved to a file it refuses to load on boot? Also be careful dying if you're playing with keyboard! The mouse cursor can vanish (read: stop working entirely) on the death screen, making you force-quit the game to reload.
I know I'm a harsh grader sometimes, but this is an honest plea from me to you: Hero Siege is a bad game made by people who are, at best, first-time developers way in over their heads. Please do not buy or support this title. It has been in enough bundles I've given out around 3-5 keys on my own now, if you MUST play it, wait for another deal of that sort. It's very bad, and not in a funny "it's better with friends" way. (Remember: online multiplayer is a DLC-only feature, so you're getting overcharged to screw around with pals who aren't at your place.) Everything it attempts is done better by another game, and most of those are just as cheap or entirely free.