I heard about Bilal & Mushtaq in Karachi. They do lot of highrises.
In the end and based on my exp, work never ends in any firm. experiences vary. But its all routine, its all typical. Self study and hard work is everywhere. But I am more interested in "work culture" and employees care. All firms are doing business, earning money, and you work for them. I have never seen/heard about a good company in Pakistan or abroad that has a nice relaxed work culture and relations for structural engineer :p. So good luck for choosing structural engineering practice.
An no one to blame, even if you open your own consulting firm, you would follow the same old boring routine...it all depends on money coming in.