1. If someone was maximizing their waits, they wouldn't choose a shorter line and queue for something longer. So in the case DAS is used for pooh, people could go get a snack, go to the bathroom, watch a parade, or quite possibly do IASW. For anybody who really likes 7DMT, they could just get a pass for that and then do Pooh and VOTLM while waiting for that time to come back up. Also remember if for some reason the guest got a pass for something that is 25 minutes and then came back 35 minutes later due to any number of reasons, they still get to go in the LL. So you can't immediately discount other lines that are similar in length from people possible targets.
2. You were saying that some queues have short waits so a person going into that queue while having a return pass doesn't make a difference. I think that is impossible as anybody behind you in those queues had to wait at least one person longer. And the overall difference on people essentially being in two queues at once is proportionally related to the number of people using that strategy. And if those former "walk on" attractions start getting longer waits from people who have nothing to do waiting for the 7DMT return time, then it cuts back on what the day guest can do without paying for G+ or ILL to make their day manageable.
3. For people who truly need DAS to make their park experience manageable, I agree that they aren't likely trying to sneak in extra rides while waiting for the 25 minute Pooh window to end. But it seems Disney has determined that a high enough percentage of people they gave DAS to are gaining an advantage over guests that don't have that accommodation. Personally I know how to maximize the line waits and get a ton done with G+, though it's somewhat unpredictable what will be available throughout the day. Given that line waits are far less predictable than which G+ time slots are left, they have created a situation where this DAS is more effective, more efficient, allows for actually planning your day ahead of time rather than just kind of winging it, costs nothing compared to $30ish per person, and ultimately impacts 40% of guests in attendance.
I think you are applying your decision engine to a static point in time and thinking about what you would do in that situation. That can't be applied to a fictional guest I will create (for this example) who lied about their anxiety to get DAS and intends to ride as many things as possible today. They could get that Pooh pass, go knock out Dumbo and meet the characters in big top, then walk back to do Pooh, then get a pass for 7DMT and ride UTS, meet ariel, ride IASW, have a snack. Then ride 7DMT, get a SM pass, do peoplemover and MILF, do Tron if they got a boarding group, ride SM. Then get a HM pass, grab a hot dog on the way, hit the Tangled restrooms, ride HM. Then get a BTMRR pass, do Tiki Room and magic carpets, do Pirates, then use the BTMRR pass. Clearly this is a hard-to-follow narrative and just a random example of what to do, but some people will maximize in this way. It's what people used to do with FP+ when they could plan certain rides at certain times and know what the line waits would likely be as the day goes on.