subfiles not detecting draft mode

Add

\makeatletter
\def\@classoptionslist{draft}
\makeatother

before the \documentclass line (while canceling out the explicit 'draft' option from your class declaration) in the main.tex to make sure that the draft option is active also in your subfile text.tex. The following one-liner is equivalent:

\bgroup\makeatletter\gdef\@classoptionslist{draft}\egroup

Obviously, once you want to change to 'final' just delete or comment out that line.

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Alternative

You can also specify the 'draft' option directly in your subfile:

\documentclass[draft,main.tex]{subfiles}

It will be discarded anyway when the subfile gets included back to main.tex (see \skip@preamble in subfiles.sty).

Important: Make sure that the parent file name is the last option as subfiles.cls lets the internal macro that saves the parents file name, i.e. \preamble@file, to the \CurrentOption inside a starred option declaration.

_{Tested with version 1.1 of subfiles from 2012/05/23.}