My 2 cents...

If you order the most expensive item on a 1 TS and 1 CS meal - then yes DDP is worth it.

Such as:
Arrosto D'Agnello Al Rosmarino - Roasted Rack & Leg of Lamb, Potatoes, Rosemary, Wine Sauce $34 at Tutto Italia, Italy
or
NY Strip Steak - Port Wine Sauce, Baked Romano Cheese Potatoes and Broccolini $28.99 at Tony's, MK
or
Oak-fired Filet of Beef - Mascarpone Potatoes, Blue Lake Beans, Arugula Oil, and Teriyaki Barbecue $47 at California Grill, Contemporary Resort
or
New York Strip - with Red Bliss Mashed Potatoes, Haricot Verts and Red Wine Sauce $28.99 at Grand Floridian Cafe,Grand Floridian Resort and Spa
or
Char-grilled Buffalo Striploin Steak - with marble potatoes, garden vegetables, and Shiraz Gastrique $43.00 at Artist Point, Wilderness Lodge

We do OOP - our reasons:
1) we eat breakfast in our room (cereal, granola bars, fruit)
2) If we do an early AM EMH - we get an ADR for a breakfast buffet.
CP (serves untill 10:30 am) & 1900 Park Fare (serves until 11:30 am) is less expensive at breakfast and will count as our lunch.
With us getting up early for an AM EMH - we go back to the resort to relax in the afternoon. We eat dinner at our resort CS (or in a Park) and then go to a Park in the late afternoon.
3) if we have done a late night EMH at a Park (MK can be open till 2 am in the summer) - we sleep in, no room service (we just get clean towels) - eat breakfast in our resort around 11 am, go to a Park and have an early dinner ADR around 4 pm, then a snack in the evening.
So only 1 TS and a snack.
4) We do not order alot of steaks. We are mostly a chicken, burger, pizza and pasta family. We skip appetizers and desserts.
With that said - it is never the most expensive items on the menu.
Our kids drink milk, DW drinks nonsweetened iced tea, and DH drinks coffee.

Examples:
In Via Napoli, Italy, EPCOT, we can get a Large pizza for $28 and and drinks for $12 - dinner costs us $40 before tax
In LLT, MK - lunch we can get burgers for $13, and pasta with chicken for $17,
drinks for $10, cost = $80 total
In 50PT, DHS - dinner we can get fried chicken and ceasar salad with chicken, with drinks, for our family of 4, cost = $80 total
In RFC, DTD or AK - dinner or lunch we can get burgers for $14, chicken sandwich for $15, DD does kids size pasta for $8 (even though she is a teen, not a big eater), again drinks would be $12., cost = $75