And you actually KNOW they are overpaid??? How? As far as I am aware, trade union officials are paid fairly modestly. Presumably the top layer of union management are more highly paid than branch officials, as would be normal in all organisations, but I doubt if they are paid as much as IBEC top management or the top manangement of large employers.
"They do very little for the workers of Ireland" Their role is to represent their members in negotiation with employers on wages, conditions, disciplinary issues, redundancy etc. At a time of recession and very high unemployment like now, employers have considerably greater power than have individual employees and trade unions can help redress this unfair imbalance. Sometimes even unions cannot win (e.g. Vita Cortex) but any employee is safer being in a union than not.