How are you defining ‘large scale surveys’?
There were no scale restrictions on V1 when I used it, how is V2 restricted?
From the Limesurvey features page:
LimeSurvey 2.x currently offers:
Unlimited number of surveys at the same time
Unlimited number of questions in a survey (only limited by your database)
Unlimited number of participants to a survey
The limit you reached seems to be at odds with the Limesurvey docs.
I haven’t used Limesurvey recently to know if it works at large scale without restrictions, maybe someone else can weigh in.