United appeared set for a third defeat in eight games in the English top flight but were rescued three minutes from time by Daley Blind, who cancelled out Saido Berahino's 66th minute strike with his first goal to give the visitors a share of the spoils.
Earlier, United substitute Marouane Fellaini opened his account to level following Stephane Sessegnon's fine opening goal for the home side but, despite Blind's late heroics, Van Gaal was disappointed not to have taken maximum points from a game in which he thought United produced their best performance of the campaign.
"I'm very disappointed because we played our best match of the season and the result is not good enough," Van Gaal told Sky Sports.
"We could have won but could have doesn't count in our world.
"We created a lot of chances and only two shots from West Brom were goals. We gave it away with our individual errors."
Van Gaal felt his defence afforded West Brom too much space but believes the players are adapting better to his philosophy in the 4-1-4-1 formation he deployed at The Hawthorns.
"They are playing more narrow in midfield and our lateral defenders have to push up, we prepared but we gave too much space," Van Gaal added.
"I'm looking for balance and maybe with this formation but with the same philosophy we could do better. The players understand better this philosophy with this formation."
Although the Dutchman is seeing improvements in United's play, he is not satisfied with their points tally of 12 from eight games.
"It's not too good. I think when we see the games, normally we are the better team," he said.
"When you have 12 points out of eight games, in my opinion it is eight points too few."
