keep in mind, crossbows cannot move and shoot. So you effectively have to find great terrain and get there first, or run the crossbows behind shields as they get into position. If your going to field Vrasku, always get him to shoot over the shoulder of another uruk, even another crossbow uruk as he has lowish defence, elves like to pin cushion him. (I think D5 with S3 bows is 5+ to wound? 2 of those and a bad fate roll and your down a hero). So take a good look at the board first. If there is no good place to set up shop, then stick with scouts and bows rather than x-bows. Oh! and if the enemy has cav, always aim your crossbows at them if you can. 4+ to wound the steed or 5+ to wound the rider is not bad odds at all.
Berserkers and ferals both are great front row hitters... but don't run them in the front row. With the same D as a regular shield uruk, enemy archers will prioritse them and take them out at range.
Don't forget about your allies! Shield uruk->spear orc->pike uruk is a cheap version of the pike blocks. A strong front and back with a juicy center, but it will save you some points. Thrydan wolfsbane is an excellent hero/monster killer. (2 attacks+cav bonus = 6 chances to wound + special rule = 12 potential wounds in 1 turn!
) Dunlanding soldiers (converted rohan models if you don't want to pay 100 USD for a warband of 12 of them) can give you a nice opportunity to add colour to your force.
Trolls? (as a rohan player) I would much rather face a troll than 10 shield uruks. 1 troll = 3 attacks and 3 wounds. 10 uruks = 10 attacks and 10 wounds.
Saruman? Also not a really big fan. He ties up alot of points and requires constant attention. Maybe our resident Isen player hasn't been playing him right so far, but so far hes been less that stellar.
Hope this helped