Chose Engineer because the main character in most games, especially this one, can be very powerful. Engineer has nice support for DPS and Tanks, giving buffs and debuffs. Combining that with the raw power that main characters can have, it just makes Engineer a very versatile class, switching between Buff Support and DPS. Combining that with Control freaks like Gila SSS or Joe Nichola SS, and an amazing healer such as (forgot his name but I think it's Robert something) SSS rank, you can easily outlive DPS teams, and tank really hard abusing his Shackle ability and Holy Sword. Throw in some DPS heroes in your formation (two more) and you're good to go. That's why I chose Engineer. So I don't have to waste a slot using a Buff Support Companion, like the 2 day login Hero.