I bet to differ, Joe. I would say it depends.
For proprietary directors, there is no "business" content in the Form 11 - it will have already been handled as part of the audited accounts of the company and remuneration will have been done through by PAYE. The Form 11 just replaces the Form 12 which would they would have used before for additional income.
Even if you are a sole trader then in many instances using an accountant can be an overkill if it's a simple business. For example I am an IT contractor and for years operated as a sole trader and paid accountants to do my trivially simple business accounts and file Form 11s for me. Like I said, most accountants don't particularly have any interest in small jobs like this and I don't blame them in the least given the hassle involved for a relatively small sum. One accountant actually told me this and instead of looking around for another accountant or paying double for the service, I learned how to do this myself.
As part of this I reviewed all the previous returns and discovered at least three basic mistakes between two accountants: one was where punt invoice amounts were recorded as euros, another overclaimed for pension contributions and another neglected to deduct accountant's expenses.
Depends on your personality I suppose but I don't mind researching these things, ringing revenue for guidance the current rules and building systems using Excel to handle my accounts. Each to their own but I suggest if you are numerically minded at all, are methodical and curious, your business is relatively simple and you're not scared by forms then it's worthwile and satisfying to learn enough about accounts and the tax system to do the return yourself.