多线程Web请求正在连续执行

我正在C#中构建一个web scraper，用于处理代理和大量请求。页面是通过ConnectionManager类加载的，该类获取代理并重试使用随机代理加载该页面，直到页面正确加载。

平均而言，一个任务需要100到300个请求，为了加快进程，我设计了一种使用多线程同时下载网页的方法。

        public Review[] getReviewsMultithreaded(int reviewCount)
    {
        ArrayList reviewList = new ArrayList();
        int currentIndex = 0;
        int currentPage = 1;
        int totalPages = (reviewCount / 10) + 1;
        bool threadHasMoreWork = true;
        Object pageLock = new Object();
        Thread[] threads = new Thread[Program.maxScraperThreads];
        for(int i = 0; i < Program.maxScraperThreads; i++)
        {
            threads[i] = (new Thread(() => 
            {
                while (threadHasMoreWork)
                {
                    HtmlDocument doc;
                    lock(pageLock)
                    {
                        if (currentPage <= totalPages)
                        {
                            string builtString = "http://www.example.com/reviews/" + _ID + "?pageNumber=" + currentPage;
                            //Log.WriteLine(builtString);
                            currentPage++;
                            doc = Program.conManager.loadDocument(builtString);
                        }
                        else
                        {
                            threadHasMoreWork = false;
                            continue;
                        }
                    }
                    try
                        {
                            //Get info from page and add to list
                            reviewList.Add(cRev);
                        }
                        Log.WriteLine(_asin + " reviews scraped: " + reviewList.Count);
                    }
                    catch (Exception ex) { continue; }
                }
            }));
            threads[i].Start();
        }
        bool threadsAreRunning = true;
        while(threadsAreRunning) //this is in a separate thread itself, so as not to interrupt the GUI
        {
            threadsAreRunning = false;
            foreach (Thread t in threads)
                if (t.IsAlive)
                {
                    threadsAreRunning = true;
                    Thread.Sleep(2000);
                }
        }
        //flatten the arraylist to a primitive
        return reviewArray;
    }

然而，我注意到，请求在很大程度上仍然是一次处理一个，因此该方法的速度并没有以前快多少。锁会引起问题吗？ConnectionManager是在一个对象中实例化的，而每个线程都从同一个对象调用loadDocument，这是事实吗？