No, more groups do not need to be investigated by the IRS, because the IRS uses its audit process in order to censor free speech. Groups trying to get non-profit status face struggles convincing the IRS that they are not too conservative to have tax-exempt status. The IRS should do it's job, not harass people.
No, I do not think that more groups need investigated by the IRS. I think that the IRS needs to calm down who they go after and that it is all political. The IRS needs to focus on just collecting taxes and not going after hard-working Americans who pay taxes.