Hi n3ntjmatt
welcome to the Apple Community.
Re: "When we get text messages when the phone is in silent (vibrate) mode, the current vibrate is barely noticeable".
Wondering if you are using "Do Not Disturb" as well as Silent ?
You might want to try turning it off / turning it on / to see what effect it has on your vibrate experience...
Eg: If the Do Not Disturb button is highlighted, you can tap it to turn off Do Not Disturb.
(When Do Not Disturb is on, its icon also appears in the status bar.)
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Re: Is this problem so hard that Apple doesn't know how to or care to fix it?
We are all Apple users, like yourself in the community.
You might want to send feedback to reach those who work behind-the scenes at Apple. They will likely not reply, yet your feedback may help with establishing just which iPhone / iOS combinations have a vibration issue. The more feedback Apple receive on an issue, the more likely we will see an update that addresses it.
Web-form for feedback: Feedback - iPhone - Apple
All the best :-)