ถือวีซ่านักเรียน Tier 4 อังกฤษ เข้า Ireland ก็ต้องทำวีซ่าท่องเที่ยวตามปกติ "แต่เว้นค่าวีซ่า" จริงหรือไม่

You haven't tried hard enough then.

http://www.inis.gov.ie/en/INIS/Pages/Irish+Short+Stay+Visa+Waiver+Programme
Click "Information Note" at the bottom of page.

http://www.inis.gov.ie/en/INIS/Information%20Note%20-%20Visa%20Waiver%20Programme%20October%202014.pdf/Files/Information%20Note%20-%20Visa%20Waiver%20Programme%20October%202014.pdf

point 15 page 5 of 8

15. I am a national of one of the countries covered but am a long-term resident in the UK or the Schengen area. Can I avail of the Programme?

Nationals of the countries above, who are long-term legal residents in the UK or the Schengen area, will still require an Irish visa but will have the visa fee waived as part of the Programme.  
The visa fee is usually €60 per person, including children, for a single visit, or €100 for a multi-entry visa.
Visa applicants will see comprehensive guidelines on making a visa application and may follow links to make an online application at:  http://www.inis.gov.ie