So in the span of one morning you have 30 open tabs from somewhere? And tabs somehow don't open and/or stay open when using another device or not using landscape mode on the iPhone 6 Plus (or you are saying they just become more visible even though they are still there basically)?
I am saying this....
On the iPhone 6 or below, you open a website and click on a link and it opens in a new tab. Somebody sends you an email or an iMessage and you click the link and another tab is opened. No problem because the tabs are always hidden in that cascade thing. Turn your phone into landscape mode and nothing much happens. Again no problem.
On the iPhone 6 Plus in landscape mode you have tabbed browsing, now you suddenly get 30-40 tabs appear at the top of the page. 80% of the tabs being unreadable because so many are open. You have no idea what will open when you click on a tab because the tab has no text on it. See my previous screenshot. Yes I can turn tabs off but they are useful when you only have half a dozen open or I can close them ONE BY ONE, but my point is Safari needs a setting to limit tabs to say 6 or whatever you set it to be.
I've had iPhones for years and this is never really been a problem until I've just upgraded to a 6 Plus and the issue is very evident.
Yes I have 30 tabs open since this morning. I do a lot of work based browsing on my iOS device.