According to R. Yosef Karo's uncle, R. Yitzchak Karo, the Sephardic practice prior to the Zohar was like the Rosh, to wear tefilin with a bracha (quoted in שו"ת בית יוסף, תש"כ, עמ' שפה). The Beit Yosef (או"ח סי' לא) cites the Rashba in addition to the Zohar, as the source for the change in Sephardic practice. It isn't clear what Sephardic practice was prior to the Rosh, however it seems likely that it was not to wear. The Otzar ha-Geonim (Eruvin 192-193) forbids tefilin. The BeHaG cites R. Yaakov ben Haviv as prohibiting (Hildesheimer ed., pp. 482-483). The Sefer ha-Ittim also prohibits wearing tefilin (cited by the Rosh, Halakhot ketanot, tefilin 16). The Meiri cites the Sephardic practice as not to wear tefilin (Moed katan 18b).
On the other hand, the sources to wear tefilin are Ashkenazi. The Sefer haTerumah proves from the fact that one can write tefilin on chol hamoed that it is a zman tefilin (hilkhot tefilin 213). The Hagaot Maimoniot says וכן הנהיגו כל רבותינו להניח תפילין בחול המועד. The Raavad (תמים דעים מ) says one is not obligated but if you want to wear, you should do so without a bracha. The Semak says to wear without a bracha (mitzva 150). The Rosh cites the Maharam as making a bracha.
All these sources are from Jacob Katz's article about the topic in הלכה וקבלה.