Don't know about Mastercard but I did have travel insurance with VISA and paid an additional €40 for 'full', bells & whistles, travel insurance. Had the policy for 3 years and made a claim for medical expenses abounting to approx. €175. Turned out that the excess was €150, so we only got €25 back. This is where these free and/or cheap insurance products catch you: high excess. Maybe Mastercard doesn't have a high excess, but check it out.
Blue Insurance have a good policy; it'll cost you just under €60 for an annual family policy if you have medical insurance coves (Quinn, VHI, Vivas etc).