None of the above solutions worked for me. This is my solution:
/* Height fix for select2 */
.select2-container .select2-selection--single, .select2-container--default .select2-selection--single .select2-selection__rendered, .select2-container--default .select2-selection--single .select2-selection__arrow {
height: 35px;
}
.select2-container--default .select2-selection--single .select2-selection__rendered {
line-height: 35px;
}