You can limit the impact of bow fire by keeping Orcs with shields at your front and spear or 2H weapon models behind them while you close. But you will take hits and losses. That's what Orcs are for.
Consider some fast troops, such as Warg Riders, to speed ahead at the archers. They will either make it and engage or become the targets themselves. Either way your Orcs aren't being shot at any more. Still, Orcs are cheap enough where you should have a lot to absorb some losses while closing ( DON'T hang back...it will not go good for you).In a fair fight, standard Orcs will take a beating in melee against all but the most basic troops. Don't fight fair. Your should have 2-3 Orcs on every model you attack. A great setup would be an Orc w/ 1H weapon and shield backed by a spear. With him is a second Orc with a 2H weapon. When you roll to Fight you will get 2 dice at normal F and one die at -1 (2H). Your opponent should only be rolling 1 die so you have a good chance to win. When you do, you have two strikes at regular Strength and one at +1 to increase the chance to wound. If facing an opponent Hero or greater troop then try to get more Orcs in there.
Also, really look for opportunities to call Heroic Combat. Orc Captains (and even some named Heroes) are relatively cheap and you should have a few scattered in your force for Stand Fast anyway. But if you can get 3 Orcs and your Captain in contact with a weak enemy troop (remember, support doesn't count for this part), call Heroic Combat. When you kill him jump all those Orcs forward to enforce other fights.
Also, keep in mind the rule of combined arms. For many forces this includes bows. For Orcs it's not as critical since they're pretty weak, but I suggest almost always to have at least some ranged fire. Instead though with Orcs you do good having a mix of stronger models in the ranks (Mordor Uruks or Morannons), Warg Riders and maybe even a Troll or two depending on points.
You say you also have Fallen Realms. I'm not sure what specifics, but Haradrim cavalry, infantry and bowmen are actually a great compliment with Orcs IMO. Perfectly themed and the Haradrim are nearly as cost effective as Orcs so you can still have very high numbers.
Also, just the simple play style of SBG is significantly different than WotR. You may in fact have a good list but just making tactical errors while playing as a result of your WotR experience. I know when I first started playing my Wood Elf army in WotR I was finding myself slaughtered in the first couple games simply because I kept forgetting that each side gets to strike blows in melee. This is NOT the case in SBG. So perhaps you are taking actions that you expect to have a certain result, or at least don't expect to, and it's biting you?
In the event it is the list, give us an idea of what type of army you are facing, as well as a few specifics of what you already own and we can offer up some better details.
