So, having worked (briefly) in the catering business, I can take a shot at this. Most of these courses would have been fairly small portions, artfully arranged on a plate to make it look attractive. The point is that you have enough money to have your staff prepare many many dishes, rather than just two or three separate items that normal people would eat at a meal.

Speaking from experience, it's in some ways easier to prepare a 12-course meal for 300 diners than a 4-course meal for 10 people. There are certain economies of scale in the prep work and cooking that you can achieve with large catered meals.

Here's the menu of the first-class menu served on the Titanic on the night of April 14th, 1912:

First Course

Hors D'Oeuvres
Oysters

Simple starters and oysters, probably on the half-shell.

Second Course

Consommé Olga
Cream of Barley

The soup course.

Third Course

Poached Salmon with Mousseline Sauce, Cucumbers

Fish course, probably a small portion.

Fourth Course

Filet Mignons Lili
Saute of Chicken, Lyonnaise
Vegetable Marrow Farci

The proper appetizer. I suspect, but cannot prove, that an individual diner would be offered only one of these, not all of them.

Fifth Course

Lamb, Mint Sauce
Roast Duckling, Apple Sauce
Sirloin of Beef, Chateau Potatoes
Green Peas
Creamed Carrots
Boiled Rice
Parmentier & Boiled New Potatoes

This is the meal itself -- several meats and sauces, peas, carrots, potatoes

Sixth Course

Punch Romaine

This is a palate-cleansing cocktail made with shaved ice and rum, and served in small cups: http://www.saveur.com/article/Recipes/Punch-Romaine-Cocktail

Seventh Course

Roast Squab & Cress

This would be a roasted squab, probably portioned (not whole!) on a bed of watercress or similar vegetables.

Eighth Course

Cold Asparagus Vinaigrette

This would be the salad, eat at the end of the meal instead of the start, as was the fashion 19th-century France.

Ninth Course
Pate de Foie Gras
Celery

A fatty palate-cleanser, probably with very small portions, again.

Tenth Course

Waldorf Pudding
Peaches in Chartreuse Jelly
Chocolate & Vanilla Eclairs
French Ice Cream

The dessert course, quite similar to what we eat for desserts today.

So, that's sumptuous, but not that excessive.

Edit: formatting.

Portions only go on the plate in service Russe which was rare before the 20th =. English-style service had everything taken diner to diner. All the fancy arrangement was on the serving tray, which diners destroyed in taking portions. French service relied on the food being on the sideboards and brought by the waiters to the table. That's 19th & 18th C. I'm weak on Early Modern dinner etiquette, but have Rickert's collection of Renaissance and Medieval books. That's an entirely different set-up, with service from one side of the narrow table rather than diners all around it.

For really big feasts, one has to consider it a sampling. As well, when there were several dishes per course, one didn't have to eat everything. Think of it like when they bring the dimsum carts around: you don't have to have one of everything.