At my university, lectures, labs, seminars and tutorials happen between 9am and 6pm, with some lecturers making themselves available outside this time for meetings with students. Obviously no lecturer has to lecture all that time with no break, but it is very silly to make assumptions about other uni's timetables based on your own.
When lecturers and staff at my university went on strike, students were asked not to cross picket lines to show solidarity with lecturers and other staff who are having pay cuts, while the vice chancellor gets a pay rise and more perks and the university continues with building works that won't benefit the majority of students. Obviously not all did, but the SU's view was that they felt that strikes are important to raise awareness of the problems with higher education in the UK.
If lecturers are not paid well, then the quality of research and university education in the UK will decline. If support staff are not paid well, then the quality of student experience will decline. There are very serious issues in UK higher education right now, especially since the current funding structure appears to be unsustainable.
Higher education in the UK is in a mess at the moment, and I think crossing the picket line in this case suggests that Tristram Hunt doesn't care about these issues. As a Labour MP, I do think he should have thought carefully about crossing any picket line. His party is funded by unions after all.
I think it was the wrong thing to do but I'm not sure it's worth him resigning over. Ironically, his actions have at least meant that the strike got more attention.