The game does ramp up but uses player controlled events, so take your time.
The game ramps up as you take down the bosses, as in it will spawn invasions if you loiter too long (random time, could be a day or a week) but the invasion types depend on what bosses you have killed.
Pre 1st boss, its just boars and necks try rush you, its more a meat buffet for most players, you will see the 'invasion' area on the mini map, its a timed event so stay in the area.