What was wrong with him? The dwarves don't really trust him with their army (at least in my cases). You usually have to chase after him. Helmar is in charge of meeting him. He always attacks within a day's travel from the first castle. Karl has the biggest army.

I measured the distance from the portal to the witch – it's 6-9 days' travel, depending on the logistics (basic – advanced), how you go, and what you pick up. Warrens is waiting by the portal, expecting the castle siege to last 2-3 days. The siege usually starts on days 25-26 out of the 30 allotted. It's extremely unlikely that he will reach the witch faster than the start of the city siege, unless Warrens is rushed (for example, led directly to the teleport, without going into the snowy area), and the siege is delayed until the last moment.
Losing days at the teleport means that, after reaching the main road, Warrens encounters a local "rush hour": all the enemy heroes with large armies hang out there. Again, he is forced to wait; he needs all the movement points to get him far enough onto a side road so that no one intercepts him. You could say, I need to go to the basement for an important reason, urgently, but I keep getting delayed.