Yeah joining a hardcore guild right at first go might be really overwhelming. You should take it easy and explore everything slowly. Take a look at the wow_dota and you'll see lots of social events organized that are open to all levels. Guildchat is also really active so there's always people to talk to if you're bored or need to ask questions.

If you want an invite, make a character and poke me on aim. My aim username's still the same as my lj name.