I think that most of us who are somewhat fairly fresh in this CC journey are learning at least some of the Hard basics.
For example in order to as you referenced, thickening the files, i took on my own fair share of new cards in 2014. The last pair in July i paid especially close attention to the FICO returns after both approvals.
My results returned boiled down to this: a clear 5 point hit each for the Inquiry (10), plus an additional 1 point drop for each of the fresh TL's (2) for a total immediate DING of (12) points. FWIW, i have 2 open CC's at only (1) year history each with another soon to follow in October. Most of the others are less then 12 months and 5 less then 6 months.
My FICO scores had just finally climbed the ladder to 715 which is been tops for me so far but the DING lowered them to it's current 703 and since i don't want to return back to the 600 club any time soon, i absolutely have to leave well enough alone (Gardening) and just manage UTIL/SPEND the rest of the way out untill time the numbers begin to go back up again.
I agree it sux, and in my case, i only have 3 more Rewards Cards needed to finish out a strategic plan set up to meet goals. In the meantime it's Limbo and sitting things out for as long as it might take to see a change in score back upward again.
This FICO scoring mania is truely painful in many ways but has it's own built-in checks & balances 
I am just now recovering from the new account dings.
Every account you see in my sig with the exception of the car loan was opened May-Dec 2013 and ALL of them pulled TU.
That's why my TU score is 20+ pts lower than the others... All the INQs. Some have aged past 1 year with the rest hitting that mark by Dec when it will be 1 year since my last new CC.
In short... I'm expecting my TU score to rebound at the end of the year. My CRA reports are the same other than the INQs flooding my TU report and dragging my score down.
