Meh. Give me quality and offensive instead. I can live juggling 3 constantly employed diplomats. And 4 relations is enough, if barely, to maintain 3 vassals and an ally, with occassional mil access for short time getting paid in diplo points.
It is not even the diplomats. On the influence side, you get 25% Discount to diploannexation and -20% AE which means faster integration and less coalitions, on the diplomatic side you have 20% province cost reduction and the stabhit reduction. The extra diplomat, diplo relations, and diplo reputation are just extra bonuses.
The only miltech idea groups that are absolutly necessary are Offensive and Defensive. Offensive for forced march and better generals, defensive for the army tradition and morale. Quality, Quantity, and Aristocratic have their perks but there is nothing about them that are 'must have'. Given they still make amazing late-game picks over most Diplomatic/Administrative idea groups.
But then again, i find humanist rather unnecessary, contrary to the common wisdom. I would rather take religious and borg into one volk, one religion state.
Humanist or Religious are both equally valid choices. Given, I like Humanist better because it saves me more monarch points over the long run with the idea cost reduction and gives me a LOT more accepted cultures. Religious is also slightly weaker in 1.8 since the religious CB got indirectly nerfed by the war leader changes.
Overall, my list of must have idea groups for 1.8 are Offensive, Defensive, Diplomatic, Influence, Innovative, and Humanist
Quality got dropped because, after the 2.5% Discipline nerf, its a lot less valuable. Hell, countries like Brandenburg and Ottomans will still stomp even without it.
Administrative got dropped because, now that vassal feeding is much easier, you never have to core anything directly, and the whole reason for Administrative is to make coring easier.
Influence and Diplomatic got added on because they make huge conquests so much easier and painless.