My main concern is getting the right damage for claw and bite attacks without making him too easy and just a bag of HP. I don't like the DMG's approach of trial and error. I want more steamlined monster building rules instead of the "fly by the seat of your trousers" ones. I'm not looking for him to be a solo per se, he is always followed by a pack of orc ghouls.
First, you need to determine whether or not your group aligns with the standard MM monsters. By this I mean the MM seems to be geared for a group of 4 average players using the Basic rules. If you allow feats, multiclassing, magic weapons, your players are optimizers, good tacticians, or more than 5 players you will probably need to buff the monsters.
Assuming you fall into the first category, it is fairly simple as each CR is given a DPR range (99-104 for CR 16). The simplest to achieve this is (remember something about a Hill giant), give it a Huge weapon. Claws typically do about 1d6 damage, so Huge claws should do 3d6. Since Huge should have at lest a Str of 22 (+6), you are looking at 16 (3d6 + 6) at least per attack However, your looking at 6 attacks per round if you want to make that work. Personally that seems like to many to me. Thus, you need to make some adjustments. Here are some options:
1) Give it a feature like the Hobgoblin's "Brute"
2) Give the claw attack a theme rider damage, such as "plus 14 (4d6) necrotic damage."
3) Give it another attack, possibly a recharge power that does high damage, conceptually like a dragon's breath weapon.
With these I use #2 or #3 the most (#1 feels a bit like cheating to me - I'm weird that way)
So, maybe:
Claw. Melee Weapon Attack: +11 to hit, reach 10 ft., one target.
Hit: 16 (3d6 + 6) slashing damage plus 14 (4d6) necrotic damage.
That gets you a DPR of 90 with 3 attacks, so basically 90% of the way their.
To get that last little bit I would give it another attack option in the form of a bonus action, reaction, or legendary action. For Huge creatues (Hill Giants) I like to give them a bonus action / reaction for making a stomp attack against a prone target. Or possible a bonus action to make a bite attack against a grappled opponent (add a grappling rider to the claw attack). To keep it really simple:
Actions:
Multiattack. The giant ghoul makes three claw attacks
Claw. Melee Weapon Attack: +11 to hit, reach 10 ft., one target.
Hit: 16 (3d6 + 6) slashing damage plus 14 (4d6) necrotic damage and if the target is a Large or smaller creature it must make a DC 19 Strength saving throw or be knocked prone.
Reactions:
Stomp. The giant ghoul makes the following attack when a creature starts it turn prone within the giant ghoul's reach.
Melee Weapon Attack: n+11 to hit, reach 10 ft., one target.
Hit: 16 (3d8 + 6) bludgeoning damage.
This gets you to 106 (technically 2 hp over CR 16, but close enough). However, since it is a reaction, I would not apply it to all 3 rounds and that will get you to 100 DPR - spot on!
Now to clarify, this is a simple monster with no means to counter ranged attacks or conditions. If you need those, then you have some more work to do! I hope that helped.
) with legendary powers, then it's easier to make CR 16. The individual attacks can be lower, and more in line with the base claw attacks of a creature that size, since it might be able to make three or 4 of them in a single round via legendary actions. 
